Difference between revisions of "903.3 Ground-Mounted Sign Supports"

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m (903.2 Ground-Mounted Signing moved to 903.3 Post-Mounted Signing: Per Traffic, revision to bring policy into substantial compliance with the 2009 MUTCD.)
 
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==903.3.1 Ground-Mounted Sign Installation==
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Signs are ground-mounted whenever possible unless mounting overhead is justified. All ground-mounted structural and sheet signs are mounted on pipe posts, wide flange (WF) fabricated steel posts, u-channel posts, perforated square steel tube posts or wood posts as shown in the standard plans.
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|'''Forms'''
 
|'''Forms'''
 
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|[[Media:903.2a Signpost Selection Guide.xls|Signpost Selection Guide]]
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|[[Media:903.2a_Signpost_Selection_Guide_2022-5-23.xls|Signpost Selection Guide]]
 
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|[http://epg.modot.mo.gov/documents/903.2aPrintableSignpostSelectionGuide.xls Printable Signpost Selection Guide for use in the field]
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|[[Media:903.2aPrintableSignpostSelectionGuide_2022.xls|Printable Signpost Selection Guide for use in the field]]
 
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'''Guidance.''' Signs should be ground-mounted whenever possible unless mounting overhead is justified or required.
  
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Cross-sections of relocated or new signs are drawn and included in the final plans.  The cross-sections are drawn to a 1" = 5' (1:50) scale to allow for scaling of quantities.  The following information is shown for each sign:  sign number, station, edge of travelway, edge of shoulder, sign dimensions, guardrail and curb locations, post configuration, all non-standard horizontal and vertical clearances, backing bars and post lengths.  Random grid lines are used to draw the cross-section and elevations are not shown.  For multiple post designs, number the posts from left to right, and use only one post design type per sign.  All cross-sections are drawn as the driver views the sign face.  Existing signs relocated to new posts and posts being used in place are shown with dashed lines.  All back-to-back signs are noted, and the far sign is shown with dashed lines.  It is not necessary to outline the foundation size since this information is noted in the standard plans.  A note is added to the cross-section if the foundation depth is greater than the minimum shown in the standard plans.  See [http://www.modot.mo.gov/business/standards_and_specs/documents/90303.pdf Standard Plan 903.03] for recommended foundation depths for various post designs and slopes.  The post stub length is shown below the finished ground line in order to scale the correct post pay length.  [[media:903.2 Example Cross Sections Apr 10.pdf|Acceptable examples of ground-mounted cross-sections]] are available.
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'''Standard.''' If signs are placed on existing supports, they shall meet other placement criteria contained in this article.   
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Whenever possible, available overhead sign support structure columns, signal poles, etc. are used to mount sheet signs.  This is less expensive and encourages cross comparisons of signal and signing plans.  Utility poles are not used to mount signs.
 
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==903.2.1 Horizontal Clearances (MUTCD Section 2A.19)==
 
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'''Standard.''' For [[903.3 Overhead Guide Sign Mounting|overhead sign]] supports, the minimum lateral offset from the edge of the shoulder (or, if no shoulder exists, from the edge of pavement) to the near edge of overhead sign supports (cantilever or sign bridges) shall be 6 ft.  Overhead sign supports shall have a barrier or crash cushion to shield them if they are within the clear zone.
 
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Ground-mounted sign supports shall be breakaway, yielding, or shielded with a longitudinal barrier or crash cushion if within the clear zone.
 
  
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'''Guidance.'''  For ground-mounted signs, the minimum lateral offset should be 6 ft. from the edge of the travelway.  If an existing shoulder is wider than 6 ft., the minimum lateral offset for ground-mounted signs should be 6 ft. from the edge of the shoulder or front face of curb.
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Utility and light poles shall not be used to mount signs as they are either not the property and maintenance responsibility of MoDOT or are not designed to carry the additional wind loading a sign adds to the structure.
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Option. In areas with space restrictions, available sign truss columns, signal poles, bridge columns, or other significant MoDOT structures, excluding roadway lighting structures, may be used to mount flat sheet aluminum signs.
  
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Where existing signs are located within 6 ft. of a utility pole, they should be relocated to provide a minimum distance of 12 ft. where practical through normal sign replacement.
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==903.3.2 Lateral Offset (MUTCD Section 2A.19)==
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'''Support.''' The minimum lateral offset is intended to keep trucks and cars that use the shoulders from striking the signs or supports, while keeping signs and object markers close enough to the roadway to be effective.  
  
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EXIT signs placed in the gore only require a 2 ft. horizontal clearance from both edges of shoulder or front face of curbs.
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'''Standard.''' Ground-mounted sign supports shall be crashworthy and meet the latest federal crash standards at the time of installation.  
  
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For divisional and channelizing islands, a 2 ft. offset should be maintained between the edge of sign and the front face of curb.  For islands with restricted width the sign should not extend beyond the curb. When signing at the nose of a 4 ft. median, a 1 ft. offset is acceptable between the edge of sign and the front face of curb.
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'''Guidance.''' The provisions below should be applied unless specifically stated otherwise in the EPG for a particular sign or object marker. For ground-mounted signs, the minimum lateral offset should be 12 ft. from the edge of the travelway. If an existing shoulder is wider than 6 ft., the minimum lateral offset for ground-mounted signs should be 6 ft. from the edge of the shoulder or front face of curb.  See [[903.2 Extent of Signing#Fig. 903.2.18.1 Examples|Figures 903.2.18.1 and 903.2.18.2]] which illustrate typical examples of the lateral offset requirements contained in this portion of the article.  
  
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Maximum clearances will depend on roadway geometrics, profiles, and cross-sections, which all affect the visibility of the sign. Sheet type and structural type signs are generally to be placed no more than 15 ft. from the edge of shoulder.
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Maximum offset will depend on roadway geometrics, profiles, and cross-sections, which all affect the visibility of the sign. Signs are generally to be placed no more than 15 ft. from the edge of shoulder.  
  
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New sign installations should be a minimum distance of 12 ft. from existing utility poles.
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Ground-mounted signs placed in a gore only requires a minimum of 2 ft. lateral offset from edges of shoulder, face of barrier walls or guard rail.  
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[[image:903.2.1 trucks.jpg|left|175px]]
 
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'''Support.'''  The minimum lateral offset is intended to keep trucks and cars that use the shoulders from striking the signs or supports.
 
  
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It is acceptable to adjust the standard horizontal clearance to obtain a better cross-section and still maintain sign effectiveness and visibility. For example, signposts are not placed in the center of ditches; therefore the horizontal clearance may be adjusted to better span a flat bottom ditch.  Existing drainage structures, pull boxes and sidewalks may also affect horizontal clearance.
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For divisional and channelizing islands, a 2 ft. lateral offset should be maintained between the edge of sign and the front face of curb. For islands with restricted width the sign should not extend beyond the curb face.  
  
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A minimum sight distance of signs should be maintained.  There should be a minimum of 60 ft.  of sight distance for each inch of letter height with a 1,000 ft. minimum for all mainline signs.  A minimum of 250 ft. of sight distance is desired for signs on conventional roads, refer to [[903.6 Warning Signs#Table 903.6.3 Warning Sign Sizes|Tables 903.6.3]] and [[903.6 Warning Signs#Table 903.6.7 Horizontal Alignment Sign Usage|903.6.7]].  When this is not possible, relocating the sign or providing additional advance signing should be considered.
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'''Option.''' Deviation from the standard lateral offset may be used if a signs effectiveness and visibility are maintained to account for variations in roadside features.  For example, to avoid placing signposts in the flow line of a ditch, avoiding drainage structures, pull boxes or sidewalks.
  
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Horizontal clearances are not noted on [[media:D-29.pdf|Form D-29]] unless they differ from the standard 6 ft. offset.
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'''Option.'''  Lesser lateral offsets may be used in business, commercial or residential areas where limited space is available to place signs due to limited right of way, sidewalks or other restrictions which keep the sign from being installed at the correct offset. In these cases, the edge of the sign may be placed up to, but not beyond the face of the curb making every effort to maximize the offset with the space available.  
  
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'''Guidance.''' All supports should be located as far as practical from the edge of the shoulder.  Exposing traffic to sign supports should be minimized by placing signs in such locations as behind existing roadside barriers or on over-crossing structures.
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'''Guidance.''' Ground-mounted sign supports should not intrude into the usable width of a sidewalk or other pedestrian facility.  
  
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A minimum sight distance of signs should be maintained.  There should be a minimum of 60 ft. of sight distance for each inch of letter height with a 1000 ft. minimum for all mainline signs.  Signs on conventional roads should have a minimum 250 ft. sight distance.  Refer to [[903.6 Warning Signs#Table 903.6.3 Warning Sign Sizes|Tables 903.6.3]] and [[903.6 Warning Signs#Table 903.6.7 Horizontal Alignment Sign Usage|903.6.7]].  When this is not possible, relocating or providing additional advance signing should be considered.
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==903.3.3 Mounting Height (MUTCD Section 2A.18)==
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'''Support.''' Installing signs at the proper mounting height is critical not only for the sign to be seen and function, but also to the functionality of the breakaway design for each type of signpost. Mounting heights are typically listed as “nominal” as it is critical to keep the signs a minimum distance above the ground, however, signs installed excessively high also have issues, such as:
  
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'''Option.'''  Where permitted, signs may be placed on existing supports used for other purposes, such as highway traffic signal supports. 
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:* Place signs outside of the drivers line of sight
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:* Place signs outside the effective range of vehicle headlights at night making signs less visible
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:* Signs mounted too tall are more susceptible to wind resulting in signs being pushed out of plumb or being blown over
  
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'''Standard.'''  If signs are placed on existing supports, they shall meet other placement criteria contained in this article.
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===903.3.3.1 Mounting Height – U-Channel, Wood, Perforated Square Steel Tube (PSST), Pipe Posts and 4 in. Square Steel Posts (MUTCD Section 2A.18)===
  
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'''Option.'''  Lesser lateral offsets may be used on connecting roadways or ramps at interchanges, but not less than 6 ft. from the edge of the travelway.  In urban areas where lateral offsets are limited, a minimum lateral offset of 2 ft. may be used.  A minimum offset of 1 ft. from the face of the curb may be used in urban areas where sidewalk width is limited or where existing poles are close to the curb.
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'''Support.'''  There are typically two mounting heights for signs on u-channel, wood, PSST, pipe posts and 4 in. square steel posts, 5 feet and 7 feet. Traditionally, the 5-foot mounting height has been applied to “rural” areas and the 7-foot mounting high applied to “urban” areas or within incorporated city limits.  However, the term “urban” has more to do with the conditions the signs are being installed within and less about being located within an incorporated city limit.  The purpose of the 7-foot mounting height is to provide clearance for passing bicycle and pedestrian traffic, making the sign more visible over parked vehicles along the roadway and permits improved sight distance to drivers permitting them to see below the sign.  
  
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'''Support.'''  [[903.1 Extent of Signing#903.1.23 Location Standardization (MUTCD Section 2A.16)|Figures 903.1.23.1 and 903.1.23.2]] illustrate some examples of the lateral offset requirements contained in this portion of the article.
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The 7-foot mounting height also applies to all freeway and expressway applications to enhance long distance visibility.
  
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It is acceptable to adjust the standard horizontal clearance to obtain a better cross-section and still maintain sign effectiveness and visibility.  For example, signposts are not placed in the center of ditches, therefore the horizontal clearance may be adjusted to better span a flat bottom ditch.  Existing drainage structures, pull boxes and sidewalks may also affect horizontal clearance.
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'''Standard.''' Standard Plans 903 shall be referenced for specific installation and mounting height details.  The details in Standard Plans 903 and EPG 903.3 Ground-Mounted Sign Supports shall apply to all signs unless specifically stated otherwise for a specific sign or object marker elsewhere in the EPG.
  
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==903.2.2 Vertical Clearances (MUTCD Section 2A.18)==
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The minimum mounting height of a sign shall be measured vertically from the bottom of the sign to the elevation of the near edge of the pavement. Minimum sign mounting heights shall be as follows:
  
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'''Standard.'''  Vertical clearances for single wide-flange and all post designs are set from the edge of travelway to the bottom of the lowest sign.  Vertical clearances for multiple wide-flange posts are set from the edge of travelway to the bottom of the lowest sign, or the length of the shortest post, whichever requirement provides the higher clearance.  Vertical clearances for different designs are shown in the standard plans.
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:* Sign located in rural areas – 5 feet,  
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:* Sign located in urban areas – 7 feet,
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:* Signs located on freeways and expressways – 7 feet.  
  
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Supports for [[903.4 Guide Signs#903.4.1.5 Legend Types|SH signs]], such as regulatory, warning and route shield markers, are designed to provide a vertical clearance of 7 ft. 0 in.  
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The length of post measured from the bottom of the sign to the ground shall also be a minimum of 5 feet. If the length of any post within a sign assembly measures less than 5 feet from the bottom of the sign to the ground, the minimum sign mounting height shall be increased to achieve the minimum 5-foot post length.  
  
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All two- and three-post signs (any LOGO sign or sign with white legend on green, blue or brown sheeting) have a minimum 7 ft. 6 in. clearance from the edge of travelway.  Also, the shortest post is a minimum of 7 ft. 9 in. above the ground line to the bottom of the lowest sign.  This will provide sufficient post length to allow hinge plate installation, provide a 7 ft. 0 in.  clearance for errant vehicle impacts, and a 6 in. field adjustment.
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'''Option.''' Signs may be installed at 5 feet within the boundaries of incorporated city limits if the all following conditions apply:
  
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Due to wide-flange post limitations, large vertical clearances of 25 ft. or more are avoided by either moving the sign or considering a truss-mounted sign.
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:* The sign is located outside of business, commercial or residential areas where there are no high densities of entrances and cross street intersections
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:* There is no on street parking
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:* There are no sidewalks with bicycle or pedestrian traffic
  
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All two- and three-wide flange post signs contain hinge plates as shown in the standard plans.  On the shortest post a vertical clearance of 7 ft. 9 in. is maintained from ground line to the bottom of the lowest sign.  This will allow sufficient length of post for a hinge point cut line 3 in. from the bottom of the lowest sign.  Maintaining this clearance on the shortest post is critical for exit gore and other signs located between roadways and have high exposure to traffic.
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If a secondary sign is mounted below the primary sign on the same signpost(s), the mounting height for the assembly, measured from the near edge of the pavement to the bottom of the secondary sign, may be 1 foot lower than the minimums listed above.
  
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'''Option.'''  The height to the bottom of a secondary sign mounted below another sign may be 1 ft. less than the height specified above.
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In cases where signs are located on steep back slopes, it may be advantageous to relocate the sign forward or back from the proposed location to an area that is flatter to avoid a sign being mounted too high.  
  
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Where signs are placed 30 ft. or more from the edge of the travelway, the height to the bottom of such signs may be 5 ft. above the level of the pavement edge with a 5 ft. minimum post length.
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'''Guidance.'''  Signs located outside of incorporated city limits that are located in areas having characteristics of an urban area, such as around businesses, heavy residential areas, areas with on street parking and areas with sidewalks which support bicycle and pedestrian traffic, should be installed at 7 feet.
  
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A route sign assembly consisting of a route sign and auxiliary signs (see Route Sign Assemblies) may be treated as a single sign for the purposes of this article.
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Route marking assemblies consisting of a route sign and auxiliary signs should be treated as a single sign for the purposes of sign mounting height.  
  
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All posts except structural posts should have a minimum clearance of 5 ft. above the driving surface with a minimum post length of 5 ft. above the ground.  The mounting height may be adjusted when supports are located near the edge of the right of way on a steep backslope.
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'''Support.''' [[903.2 Extent of Signing#Fig. 903.2.18.1 Examples|Fig. 903.2.18.1]] illustrates typical examples of the mounting height requirements contained for signs installed on U-Channel, Wood, PSST and Pipe Posts.
  
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'''Support.'''  Without this flexibility regarding steep backslopes, a decision to relocate the sign closer to the road could be made, which might be less desirable.
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===903.3.3.2 Mounting Height – Wide Flange (I-Beam) Posts (MUTCD Section 2A.18)===
  
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==903.2.3 Pipe Posts==
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'''Support.'''  Installing signs at the proper mounting height is critical not only for the sign to be seen and function, but also to the functionality of the breakaway design. Proper mounting height is more critical for breakaway function on Wide Flange posts compared to all other posts due to the hinge component of this post design.  As with the other post types, mounting heights for Wide Flange posts are listed as “nominal” as excessive mounting heights have the same negative effects for these installations as exists with the other post types.  Wide Flange post mounting heights are greater than other posts, so in areas with back slopes it is recommended to seek out a flatter location in advance or downstream of the original installation to keep the sign as low as possible. 
  
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Steel pipe posts are used for [[903.4 Guide Signs#903.4.1.5 Legend Types|sheet (SH) signs]] up to 30 ft<sup>2</sup>.  Available pipe size inside diameters are 2-1/2 in., 3 in. and 4 in.  Post sizes are determined using the [[Media:903.2a Signpost Selection Guide.xls|Signpost Selection Guide]].  A [http://epg.modot.mo.gov/documents/903.2aPrintableSignpostSelectionGuide.xls printable Signpost Selection Guide for use in the field] is also available.  It is recommended to provide a two-post design for sheet sign widths greater than 3 ft. 6 in. (other than diamonds or the 48 in. and 60 in. Yield).  The extreme width sign, W, is calculated as: W = (area of signs + area of exposed backing bars + area of post above bottom of sign)/(extreme height of sign).  For additional information, consult the [[Media:903.2a Signpost Selection Guide.xls|Signpost Selection Guide]] (signpost calculator).
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Minimum mounting heights for Wide Flange post installations are not related to rural or urban classifications, but are directly related to how the breakaway system functions.  Standard Plans 903 provides details on the nominal mounting heights on wide flange posts.  Key details to focus on are:
  
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It is desirable to keep posts out of the ditch flow line, when possible.
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:* No wide flange post can be shorter than 7’ 9” measured from the hinge to the top of the stub.
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:* The hinge point is always below the lowest sign which is attached to the wide flange post.
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:* Nominal mounting heights vary depending if there is one sign mounted on the posts or two.
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:* For signs located in areas of back slopes, the minimum mounting height may have to be increased, or the sign installed in a different location, in order to achieve the minimum post length of 7ft. 9 in.
  
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Breakaway assemblies are required on all pipe posts, regardless of location.  Multi-direction assemblies are also required and are noted on [[media:D-29.doc|Form D-29]].
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==903.3.4 Ground-Mounted Sign Support Selection==
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'''Support.'''  The majority of MoDOT signs are installed and supported on one of 5 types of ground-mounted sign supports or signposts.  The selection of signpost is based on many factors, but primarily on the size of sign being installed and the type of roadway the sign is being installed along.  There is some overlap in signpost applications; more than one signpost may be applicable to a given installation.  The final selection of the post type is based on the attributes needed for a support as discussed in each classification of signpost below.
  
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The standard plans show design data for computing the weights (masses) of pipe posts, along with data for computing footing quantities.
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The number of posts needed to support a sign is primarily based on the width of a sign.  Typically, signs 48 inches wide and wider are installed on two or more posts.  This requirement is based on two factors, the capacity of the post and the long-term stability of the assembly.  A wide sign installed on one post will place a torsional force onto a post and in windy conditions can result in an assembly not staying plumb and, in some cases, an actual failure of the post itself.
  
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==903.2.4 Wide Flange (WF) Posts==
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'''Standard.'''  The selection of the proper size of signpost shall be based on the Signpost Selection Guide listed above. These tools will specify if a post type has the capability to support the sign in question and then specify what size post is required based on the requirements of the installation.  Before the correct size of PSST or Wide Flange post can be selected, the length of the longest post must first be determined.  To determine this, the offset and mounting height must first be determined.   
  
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WF posts are used for mounting signs larger than 30 ft<sup>2</sup>.  The post design number is determined from [[Media:903.2a Signpost Selection Guide.xls|Signpost Selection Guide]] when a sign is mounted alone or with an exit panel above the main sign. A [http://epg.modot.mo.gov/documents/903.2aPrintableSignpostSelectionGuide.xls printable Signpost Selection Guide for use in the field] is also available.  The extreme width sign, W, is calculated as: W = (area of signs + area of exposed backing bars + area of post above bottom of sign)/(extreme height of sign).
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===903.3.4.1 U-Channel Posts===
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'''Support.''' MoDOT utilizes two primary sizes of U-Channel Posts, a 3 lb/ft high carbon, rerolled rail steel post for sign installations and a low carbon steel 1 lb/ft post for road side delineation.
  
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For post designs Nos. 3, 4, 5 and 6 having weights greater than 18 lbs/ft., posts shall be spaced at least 7 ft. apart.  For post designs Nos. 1 and 2, posts may be spaced less than 7 ft. apart.  Do not use three No. 1 or 2 posts with a sign width of less than 10 ft. 6 in.
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U-channel posts can be used to support MoDOT’s small signs, such as no parking signs, object markers and chevrons on two lane roadways. U-channel posts are typically not suited to support larger permanent signs as they have limited torsional rigidity and have less ability to hold a larger sign steady in windy conditions.  These are typically the most economical posts to use to support smaller signs and given these types of signs tend to be installed closer to the roadway their ability to yield more easily to impacts means they pose less of a damage risk to vehicles.  U-channel posts are typically installed by driving the post into the ground without a stub or anchor, however, there is a stub / post installation option available which is detailed in the standard plans.
  
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In many cases, two designs are possible using a two- or three-post design chart.  There are no special criteria for determining which of these two designs to use.  Generally, signs from 6 to 17 ft. wide will be designed for two posts, while signs wider than 17 ft. requires three posts.  It is desirable to keep posts out of the ditch flow line and median, when possible.  This may be a deciding factor for a two- or three-post design.
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U-Channel posts are considered breakaway with no additional breakaway devices needing to be added.  While there are breakaway devices available for U-channel posts, MoDOT’s use of this type of post for smaller signs typically doesn’t justify their use.  A U-channel post’s breakaway is typically a yielding function, meaning as a vehicle impacts the assembly, the post yields and lies down in front of the vehicle so it can pass over the assembly.  
  
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While pipe posts are cheaper, a single WF post can support side-by-side route marker assemblies. Normally a number one WF post design will support a side-by-side assembly.  For larger two-post sign design combinations consult the [[Media:903.2a Signpost Selection Guide.xls|Signpost Selection Guide]].  The next higher post design is used when in doubt.
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'''Standard.''' U-channel posts shall be installed in accordance with the details found in Standard Plans 903. Signpost selection tools shall be used to determine sign sizes U-channel posts can support and the number of posts needed.
  
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[http://www.modot.mo.gov/business/standards_and_specs/documents/90303.pdf Standard Plan 903.03] shows data needed for computing the weights (masses) of WF posts, along with data to compute footing quantities.
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===903.3.4.2 Wood Posts===
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'''Support.''' MoDOT’s specs permit three sizes of wood posts to be used: 4 in. x 4 in., 4 in. x 6 in., or 6 in. x 6 in. MoDOT’s wood posts are pressure treated to promote longer life and resist rot and insect damage.   Wood posts were once MoDOT’s primary post to support signs on two lane roadways; however, due to issues with material stability PSST posts have become MoDOT’s standard post.
  
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Breakaway assemblies are required on all WF posts, regardless of location and are noted on Form D-29 (see Figure 8-03.4).  Multi-direction assemblies are not available for WF footings.
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When used, wood posts are capable of supporting most sign assemblies on two lane roadways, from route marker assemblies, speed limit signs, warning signs and distance and destination signs.  The use of a high quality wood post and proper installation is the key to a successful installation.
  
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==903.2.5 U-Channel Posts==
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'''Guidance.''' The continued use should take into consideration the special characteristics listed in EPG 903.3 Ground-Mounted Sign Supports.
  
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These supports are galvanized 3 lb. (1.4 kg) steel posts used primarily for installing [[903.4 Guide Signs#903.4.1.5 Legend Types|SH signs]].  Details of these posts are shown on Standard Plan 903.03. The number of posts to be used is based on the sign area for each installation and is calculated from the Post Size Requirements Table in [http://www.modot.mo.gov/business/standards_and_specs/documents/61610.pdf Standard Plan 616.10].  The [[Media:903.2a Signpost Selection Guide.xls|Signpost Selection Guide]] is also available.  Use of these posts should be based on discussions with district Traffic.  These posts are paid for by the linear foot.  No additional payment will be made for hardware.
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Proper installation is also critical for the stability of the sign assembly. The wood post should be placed a minimum of 36 inches into the ground, deeper for larger signs or in areas where the soil is weak or sandy, to keep the signpost plumb.  When backfilling the hole, material should be added in lifts, or levels, in order to properly compact the backfill.  Loose or fine materials, such as sand, sandy soil or dry concrete mix typically will not provide a long term solid backfill and can result in the post falling out of plumb over time.  
  
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==903.2.6 Wood Posts==
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MoDOT’s specifications should be followed when purchasing wood signposts.  These specifications address a posts load capacity, breakaway attributes and the compatibility between the pressure treatment chemicals and our aluminum signs and sign hardware.    
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[[image:903.2.6.jpg|right|250px]]
 
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These supports are pressure treated 4 in. x 4 in., 4 in. x 6 in. or 6 in. x 6 in. wood posts used primarily for installing [[903.4 Guide Signs#903.4.1.5 Legend Types|SH signs]].  Details of these posts are shown on [http://www.modot.mo.gov/business/standards_and_specs/documents/90303.pdf Standard Plan 903.03].  The number of posts to be used is based on the sign area for each installation and is calculated from the Post Size Requirements Table in Standard Plan 616.10. Use of the [[Media:903.2a Signpost Selection Guide.xls|Signpost Selection Guide]] is available as is a [http://epg.modot.mo.gov/documents/903.2aPrintableSignpostSelectionGuide.xls printable Signpost Selection Guide for use in the field]. Use of these posts should be based on discussions with district Traffic.  These posts are paid for by the linear foot.  No additional payment is made for slotting the larger posts or for hardware.
 
  
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==903.2.7 Perforated Square Steel Tube Posts==
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'''Option.'''  While the soil originally removed from the hole can be used to back fill around the post other alternatives may be used, such as smaller quarry rock with the crushing fines mixed in, concreted mix or expanding polyurethane foam.  
  
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These supports are galvanized 2 in. square 12 gauge steel posts used primarily for installing [[903.4 Guide Signs#903.4.1.5 Legend Types|SH signs]]. Details of these posts are shown on Standard Plan 903.03. The number of posts to be used is based on the sign area for each installation and is calculated from the Post Size Requirements Table on [http://www.modot.mo.gov/business/standards_and_specs/documents/61610.pdf Standard Plan 616.10].  Use of the [[Media:903.2a Signpost Selection Guide.xls|Signpost Selection Guide]] is available as is a [http://epg.modot.mo.gov/documents/903.2aPrintableSignpostSelectionGuide.xls printable Signpost Selection Guide for use in the field].  Use of these posts should be based on discussions with district Traffic.  The actual posts are paid for by the linear foot.  An additional [http://www.modot.mo.gov/business/contractor_resources/biditemslisting.htm bid item] must be included for the anchor sleeve, paid for by the linear foot, for each post used.  No additional payment will be made for hardware.
+
'''Support.'''  Wood posts are considered breakaway without an add-on breakaway device; however, some sizes of post do need special preparation. 4 in. x 4 in. wood post are considered breakaway without any special modifications; however, 4 in. x 6 in. and 6 in. x 6 in. posts must be cross drilled at the base to weaken them so they will break away.   The size of the holes and where they are drilled is critical to these posts meeting breakaway requirements. The details for these holes are found in the Standard Plans 903, it is important to note these breakaway holes are drilled in the sides of the post, not in the front of the post where the sign is mounted.
  
−
==903.2.8 Secondary Sign Supports==
+
'''Standard.'''  If wood posts are used, the proper size and number of posts shall be determined by using the post selection tools. 
 +
[[image:903.3.7.jpg|thumb|center|700px|<center>'''Fig. 903.3.4.2, Details for Wood Posts Requiring Breakaway Design'''</center>]]
 +
'''History.'''  One of the earliest issues experienced with wood posts is their tendency to warp and twist, both before and after installation.  Keeping a sign plumb and appropriately oriented to the roadway is critical to maintain the sign’s legibility and night time retroreflectivity performance.  This aspect of wood posts resulted in significant waste of inventory when the posts warped and twisted before being used and increased work load on signing crews who had to correct warped and twisted posts after installations.  Another concern with the use of wood posts was the installation required a hole to be dug, the posts set and property back filled so the sign would remain upright.  If soil conditions prohibited a hole being dug deep enough or the back fill not capable for being compacted sufficiently the assembly would fall out of plumb.  Along with these installation aspects, a wood post sign assembly can be very heavy, especially when the pressure treated wood is still wet with the pressure treating fluids and this can result in the need for additional people to set the post and/or increased risk of injury setting the post by hand.
  
−
These supports are aluminum wide-flange posts used to attach service signs and exit number panels to structural signs.  Details of these posts are shown in the standard plans.  There is no direct bid for these posts.
+
Towards the end of MoDOT’s reliance on wood posts a new issue was identified relating to the more environmentally friendly treatment process called ACQ (Ammoniacal Copper Quaternary).  ACQ replaced CCA (Chromated Copper Arsenate) for residential applications as CCA had chemical component which were not recommended for routine contact with skin.  However, unlike CCA, ACQ (especially early versions) turned out to be very corrosive to metals, especially to aluminum.  This corrosive nature requires special fasteners to resist this corrosive effect.  Early applications of ACQ in other states realized serious sign corrosion to the point the sign would fall off the post in a matter of a few years.  While it appears this has improved, special fasteners with special protective coatings are still recommended for use with ACQ posts.  As a result, ACQ posts do not meet MoDOT’s specifications and should not be used to support signs.  CCA treated posts are still MoDOT’s standard for wood posts, however, it is not commonly available at local home improvement centers and at many lumber yards.  Due to MoDOT’s limited use of this product contract purchasing typically is not economical or possible.
  
−
==903.2.9 Backing Bars==
+
===903.3.4.3 Perforated Square Steel Tube Posts (PSST)===
 +
'''Support.'''  MoDOT utilizes two sizes of PSST posts, 2 in. and 2.5 in., both being made from 12-gauge steel.  PSST became MoDOT’s standard post for most sign installation applications on two lane roadways in the early 2000’s, replacing wood posts.  PSST usage has since expanded to some applications on freeways and expressways.
  
−
Backing bars support wide [[903.4 Guide Signs#903.4.1.5 Legend Types|SH signs]] and side-by-side route assemblies.  The standard plans show requirements for backing bars and additional information is given in [[903.18 Preparation of Sign Plans#903.18.3 Computation of Quantities|EPG 903.18.3.8]].  Lengths and the weight per foot of backing bars are shown in the standard plans.  Backing bars are totaled and included in the bid item for structural steel posts.  Backing bars are totaled on [[media:D-29.doc|Form D-29]].
+
Unlike U-channel or Wood posts, PSST utilizes a ground anchor, or footing, within which the post is then placed.  MoDOT has several options in its specifications with respect to ground anchor/foundation systems, the use of each option is heavily based on the soil condition.
  
−
==903.2.10 Hinge Plates==
+
The anchor/footing types for PSST are:
  
−
[[image:903.2.10 Hinge Plate.jpg|right|275px]]
+
:* 12-Gauge PSST Anchor – this is the basic direct-driven anchor for 2 in. PSST posts. A 12-gauge anchor does not exist for 2.5 in. PSST posts. 
 +
:* 7-Gauge Anchor – this is a heavy wall box tube anchor which is the basic direct-driven anchor for 2.5 in. PSST posts. It is also an optional heavy anchor for 2 in. PSST posts in rocky ground where a 12-gauge anchor may deform when driven.  The 7-gauge anchor is also the anchor that must be used when installing a concrete or polyurethane footing. 
 +
:* Omnidirectional, or stabilization, Anchor – this is the appropriate 12-gauge or 7-gauge direct-driven anchor with 4 soil stabilization plates added to the anchor to increase soil surface area to help keep signs plumb in weaker soils and/or in windy areas. A JSP will be needed to specify this anchor type on a project.   
 +
:* Concrete Footings – In some applications it may be desired to install a concrete footing for PSST, similar to the footings for Pipe Post or Wide Flange Post.  Concrete footings provide a stronger foundation compared to the directly-driven anchors listed above.  A concrete footing may also be required in cases where the ground is too hard or rocky to direct drive the anchor and a hole may need to be dug in order to install the anchor.  All concrete footing installations use a 7-gauge anchor (that only has holes at the top of the tube) because concrete would flow through the holes of a normal 12-gauge PSST anchor.
 +
:* Polyurethane Foam Footings – This is an alternate to a concrete footing for PSST post installations.  This permits the footing and the sign to be installed in one trip compared to concrete, which requires a second trip to allow the concrete to cure.  The installation requirements for an expanding foam footing are the same as a concrete footing except for the diameter of the footing, which is smaller.  It is important to make sure the expanding foam used meets MoDOT specifications as not all foam products are acceptable to support a breakaway sign.  
  
−
Hinge plates are installed on all multiple post WF post designs as shown in the standard plans.  Hinge plate cut lines are 3 in. below the bottom of the lowest sign.  The cut line is a minimum of 7 ft. 6 in. above the ground line on the shortest post.  No direct pay is made for hinge plates.
+
{| class="wikitable" style="text-align: center", align="right"
−
 
+
!colspan="7"|POST AND ANCHOR DATA TABLE
−
==903.2.11 Breakaway Assemblies==
 
−
 
 
−
Breakaway assemblies are provided for all ground mounted pipe post and WF post designs regardless of location.  Breakaway assembly details are shown in the standard plans and additional information is given [[903.18 Preparation of Sign Plans#903.18.3 Computation of Quantities|for preparation of sign plans at EPG 903.18.3.7]]and at [[903.14 Sign Supports#903.14.1 Breakaway Design and the Signpost Selection Guide (MUTCD Section 2K.01)|EPG 903.14.1 for sign support]] information.  Breakaway assemblies are totaled on [[media:D-29.doc|Form D-29]].
 
−
 
 
−
Breakaway assemblies are not required for U-channel or wood posts.  For perforated square steel tube posts, though, a breakaway design may or may not be required depending on the configuration of the posts.  The [[Media:903.2a Signpost Selection Guide.xls|Signpost Selection Guide]] should be referenced to make an appropriate determination.   
 
−
 
 
−
==903.2.12 Orientation (MUTCD Section 2A.20)==
 
−
 
 
−
'''Support.'''  The brightness of the sign may drop 24 percent when the normal offset from edge of travelway is increased to 30 ft.  The legibility remains at an 80 percent level or higher when using the standard 6 ft. offset.  The skew angle shown on the standard plans is valid for signs on tangent sections of road regardless of offset distance.  The skew angle may be adjusted to maintain brightness and avoid glare for signs on curved sections of road.  The plans indicate which signs require a skew angle other than that shown in the standard plans.
 
−
 
 
−
'''Guidance.'''  Unless otherwise stated in this article, signs should be vertically mounted at right angles to the direction of, and facing, the traffic that they are intended to serve.
 
−
 
 
−
Where mirror reflection from the sign face is encountered to such a degree as to reduce legibility, the sign should be turned slightly away from the road.  Signs that are placed 30 ft. or more from the pavement edge should be turned toward the road.  On curved alignments, the angle of placement should be determined by the direction of approaching traffic rather than by the roadway edge at the point where the sign is located.
 
−
 
 
−
'''Option.'''  The standard skew angle is 93 degrees.  However, skew angle may be adjusted to maintain brightness and avoid glare for signs on curved sections of road.
 
−
 
 
−
==903.2.13 Sign Identification Decal (MUTCD Section 2A.20a)==
 
−
 
 
−
'''Standard.'''  Every MoDOT sign, regardless of the type or style, shall have an ID on the sign.  At the time of installation of the new sign, the year and month shall be indicated.
 
−
 
 
−
'''Support.'''  The Sign Production Center is currently silk screening or placing these IDs on the front side in the lower right hand corner of the sign.
 
−
 
 
−
==903.2.14 Post and Mountings (MUTCD Section 2A.21)==
 
−
 
 
−
'''Standard.'''  Signposts, foundations, and mountings shall be so constructed as to hold signs in a proper and permanent position, and to resist swaying in the wind or displacement by vandalism.
 
−
 
 
−
Plastic/nylon washers shall be used between the heads of all twist fasteners (such as screws, bolts or nuts) and the sign sheeting to protect the sheeting from the twisting action of the bolt heads.  Plastic/nylon washers are available through the Sign Production Center at no charge to the district.
 
−
 
 
−
'''Support.'''  The latest edition of AASHTO’s Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals contains additional information regarding posts and mounting (see [[903.19 Highway Signing General Information#903.19.11 Relation to Other Publications (MUTCD Section 1A.11)|EPG 903.19.11.2]] for AASHTO’s address).
 
−
 
 
−
'''Option.'''  Where engineering judgment indicates a need to draw attention to the sign during nighttime conditions, a strip of retroreflective material may be used on regulatory and warning sign supports.
 
−
 
 
−
'''Standard.'''  If a strip of retroreflective material is used on the sign support, it shall be at least 2 in. in width, it shall be placed for the full length of the support from the sign to within 2 ft. above the edge of the roadway, and its color shall match the background color of the sign, except that the color of the strip for the YIELD and DO NOT ENTER signs shall be red.
 
−
 
 
−
==903.2.15 Ordering Signs (MUTCD Section 2A.21a)==
 
−
 
 
−
'''Support.'''  Standard signs are those signs, which are described in EPG 903.  They have been defined for size and message and given a specific sign number.  Standard signs are typically made of a single piece of flat aluminum.  Examples of standard signs are STOP signs, YIELD signs, SPEED LIMIT signs and alignment signs.
 
−
 
 
−
Structural signs are those signs that are constructed using extruded aluminum panels.  These signs are typically erected on steel breakaway posts or on overhead trusses.  Structural signs are typically found on the interstate, freeway and expressway systems.  Typical structural signs are EXIT signs (E5-1) and the EXIT DIRECTION signs (E4-1) found on freeways.
 
−
 
 
−
Roll-up signs are signs that are made on a flexible, reflective material.  They are primarily used for short-term traffic control signs for maintenance operations.
 
−
 
 
−
Signs not listed in this article are considered special signs.  See Figure 903.2.15 for Special Sign Requisitioning Process flowchart.
 
−
 
 
−
When ordering signs, there are several optional features available.  These features are primarily related to vandalism control and are the following:
 
−
 
 
−
Protective Film: It is our intent to provide a system that will allow for the cleaning and removal of graffiti, dust and pollution from the sign surface.  A protective overlay film is durable, solvent resistant and completely transparent.  At this time, the cost to apply this film to all signs is prohibitive.  If the district has certain locations that require sign replacement due to paint or graffiti, this film will allow the sign to be cleaned instead of replaced.  Contact the SPC for information on the cost and benefits of the protective film.
 
−
 
 
−
Plastic Signs: In areas where there is a problem with theft of aluminum signs, it is possible to make standard ground mount signs on a plastic blank.
 
−
 
 
−
'''Standard.'''  A requisition shall be submitted when ordering signs.  General Services form E-82 shall be completed with the quantity, sign number, size and description indicated for each sign ordered.  If the sign is needed on a rush or priority basis, this should be clearly indicated on the requisition.
 
−
 
 
−
An electronic requisition for structural signs shall be accompanied with detailed drawings of the required signs each on a separate page.  Information for these signs shall include sign legend and roadway type.  It shall also include on the requisition whether the signs are shoulder-mounted or overhead-mounted signs.  If the signs have any pre-existing size restrictions, this shall also be noted on the requisition.  If the district requires knowledge of the exact size of signs prior to fabrication, this shall be noted on the requisition.
 
−
 
 
−
Figure 903.2.15. Special Signs
 
−
 
 
−
Traffic shall approve all requisitions for special signs before fabrication.  Special signs shall be on a separate requisition from in order to reduce delay in shipping, other sign types while the special sign is being reviewed.  If a special sign is required, a description of the sign including color information, the sign's proposed location, and the reason for its use should be forwarded to Traffic for approval. 
 
−
 
 
−
At the time of manufacturing, a detailed drawing of these special signs shall be forwarded to the district.  The SPC will produce annually a listing of approved special sign numbers and legends.
 
−
 
 
−
'''Guidance.'''  If the structural sign is a replacement for an existing sign, dimensions of the existing sign should be provided if possible.  After fabrication a detailed drawing of the sign should be forwarded to the district sign shop that should be retained for future reference.
 
−
 
 
−
General Services orders roll up signs on a yearly basis.  A requisition is to be submitted by the district.
 
−
 
 
−
If either of the two vandalism control features is needed on a sign it should be clearly indicated on the sign requisition.
 
−
 
 
−
The SPC will ship the sign order to the district, and upon receipt of a sign order, the district should inspect the signs for damage and to verify the quantities, types and legends of the signs.  If problems with the order are found, the district should notify the SPC of the problems. 
 
−
 
 
−
'''Option.'''  The special sign request may include a sketch of the proposed sign and/or a picture of the problem location.  A plan for evaluating the effectiveness of the special sign may be requested by Traffic.
 
−
 
 
−
==903.2.16 Signing Paid for by Others (MUTCD Section 2A.21b)==
 
−
 
 
−
'''Support.'''  Under various policies, including Traffic Generator Signing, Custom City Limit Signing and College Signing, standard signs may be installed at the cost of the requesting party.  See Figure 903.2.16.1 for flowcharts outlining the process for a new sign request and signing already in place.
 
−
{|style="padding: 0.3em; margin-left:15px; border:1px solid #a9a9a9; text-align:center; font-size: 95%; background:#f5f5f5" width="160px" align="right"
 
−
|-
 
−
|'''[[Media:903.2.16 TR15 process.doc|TR 15 Contract Process]]'''
 
−
|}
 
−
 
 
−
'''Standard.'''  Once the exact legend, quantity and location of the necessary signing is known, Traffic shall prepare an estimate for the cost of installation.
 
−
 
 
−
If the requesting party agrees to the cost estimate, a TR-15 contract shall be executed between the district engineer and requesting party.  Upon execution of the TR-15 contract, the requesting party shall remit the full amount to the district.  All funds shall be made payable to “Director of Revenue – Credit Road Fund”.  If applicant requires a MoDOT invoice for payment, the district shall contact the Controller’s Office at the Central Office for assistance and use the [[media:903.2.16 Interagency Invoice Request Dec 2009.xls|Interagency Invoice Request Form]].
 
−
 
 
−
Upon receipt of the funds, the signs shall be ordered and scheduled for installation.  The district traffic office shall forward the funds to the district Business and Benefits personnel, along with the proper coding to ensure proper reimbursement to the district traffic budget.
 
−
 
 
−
 
 
−
====<center>Table 903.2.16 [[media:903.2.16 Interagency Invoice Request Dec 2009.xls|Interagency Invoice Request Form]]</center>====
 
−
 
 
−
{| border="1" class="wikitable" style="margin: 1em auto 1em auto"
 
−
|+
 
−
|colspan="4"|<center>''Signs Paid for by Applicant (TR-15 Contract)''</center>
 
−
|-
 
−
|colspan="4"|<center>''New Signing Request''</center>
 
−
|-
 
−
!style="background:#BEBEBE"|Step!! style="background:#BEBEBE"|Applicant Action!! style="background:#BEBEBE"|District Action!! style="background:#BEBEBE"|Central Office Action
 
−
|-
 
−
|align="center"|'''1'''||Contacted by entity||align="center"|- ||align="center"|-
 
−
|-
 
−
|align="center"|'''2'''||align="center"|-  ||District determines whether applicant qualifies for signing.  If '''NO''', district explains other options - Logos/TODS; if '''YES''', proceed to Step 3.||align="center"|-
 
−
|-
 
−
|align="center"|'''3'''||'''NO''' - Applicant can pursue Logos or TODS||'''YES''' - District requests sign details/costs from Traffic Div. (used for Exhibit A of TR-15 Contract).||align="center"|-
 
−
|-
 
−
|align="center"|'''4'''||align="center"|-  ||align="center"|-  ||Traffic Div. completes Exhibit A of contract showing sign layout, size and costs and returns to district.
 
−
|-
 
−
|align="center"|'''5'''||align="center"|-  ||District completes Exhibit A with quantity of each sign and Exhibit B with sign locations(s).  District will complete all other information in TR-15 Contract and send it to applicant for review and signature.||align="center"|-
 
−
|-
 
−
|align="center"|'''6'''||If approved, applicant signs and returns contract to district.||align="center"|-  ||align="center"|-
 
−
|-
 
−
|align="center"|'''7'''||align="center"|-  ||District sends contract signed by applicant to Traffic Div.||align="center"|-
 
−
|-
 
−
|align="center"|'''8'''||Applicant may submit payment with contract if applicant doesn't require an invoice.||District determines whether applicant will need an invoice to make payment.  If so, district will email Interagency Invoice Request to "SignContracts" group.||align="center"|-
 
−
|-
 
−
|align="center"|'''9'''||align="center"|-  ||align="center"|-  ||Traffic Div. reviews contract and  forwards to Chief Counsel Office/Commission Secretary for approval and execution.
 
 
|-
 
|-
−
|align="center"|'''10'''||align="center"|-  ||align="center"|-  ||Chief Counsel Office/Commission Secretary sends contract back to Traffic Div.  If executed, Traffic Div. proceeds to Step 12.  If not, Traffic Div. will work with district for further handling.
+
|ROWSPAN="2"; COLSPAN="2"|POST
 +
|ROWSPAN="2"; COLSPAN="2"|ANCHOR
 +
|COLSPAN="3"|BREAKAWAY REQUIRED
 
|-
 
|-
−
|align="center"|'''11'''||align="center"|-  ||District receives rejected contract for corrections and, returning to Step 5, proceeds.||align="center"|-
+
|COLSPAN="3"|NUMBER OF POSTS
 
|-
 
|-
−
|align="center"|'''12'''||align="center"|-  ||align="center"|-  ||Traffic Div. receives executed contract and sends copy to Controller's Office (<u>with interagency invoice if one was submitted</u>) and notifies district that the contract was executed.
+
|GAUGE
 +
|SIZE
 +
|GAUGE
 +
|DIMENSIONS
 +
|1
 +
|2
 +
|3
 
|-
 
|-
−
|align="center"|'''13'''||align="center"|-  ||District notifies applicant that the contract was approved/executed.||align="center"|-
+
|ROWSPAN="2"|12
 +
|ROWSPAN="2"|2" x 2"
 +
|12
 +
|2.25" x 2.25" x 36"
 +
|NO
 +
|NO
 +
|YES
 
|-
 
|-
−
|align="center"|'''14'''||align="center"|-  ||align="center"|-  ||Controller's Office receives executed contract and invoices applicant if Interagency Invoice Request was received.
+
|7*
 +
|2.5" x 2.5" x 36"
 +
|NO
 +
|NO
 +
|YES
 
|-
 
|-
−
|align="center"|'''15'''||If invoiced, applicant submits payment to Controller's Office. If not invoiced, applicant submits payment to district if payment was not submitted earlier.||align="center"|-  ||align="center"|-
+
|12
 +
|2.5" x 2.5"
 +
|7
 +
|3 x 3 x 36"
 +
|NO
 +
|YES
 +
|YES
 
|-
 
|-
−
|align="center"|'''16'''||align="center"|-  ||District receives payment from applicant and sends it to Controller's Office while also copying Traffic Div. - OR - District gets receivable report from Controller's Office showing applicant paid invoice.||Controller's Office can notify Traffic Div. if payment was received or the receivable report will show status of payment.
+
|12
−
|-
+
|(2.5"x2.5")+(2.25"x2.25")
−
|align="center"|'''17'''||align="center"|-  ||District requisitions signs and SPC produces and ships necessary signs.||align="center"|-
+
|7
−
|-
+
|3 x 3 x 36"
−
|align="center"|'''18'''||align="center"|-  ||District installs signs and '''notifies Traffic Div. of installation date''' by email to "SignContracts" group.||align="center"|-
+
|YES
−
|-
+
|YES
−
|align="center"|'''19'''||align="center"|- ||align="center"|- ||Traffic Div. notifies Controller's Office of installation date by indicating the date on the top of the first page of the contract.  Traffic Div. sends copy of completed contract to district and one copy to the applicant.  Traffic Div. will send email notification to district that contract has been mailed to applicant for the district's records. 
+
|YES
−
|-
+
|+ style="caption-side:bottom; font-size:.9em"|* TO BE USED WITH CONCRETE FOOTINGS OR IS AN OPTION IN ROCKY SOIL CONDITIONS
−
|align="center"|'''20'''||align="center"|-  ||District maintains signs as required by sign log inspections.||Controller's Office records sign contract data in receivable report and installation date for 10-year maintenance.
 
 
|}
 
|}
  
−
==903.2.17 Contract Signing Field Checks (MUTCD Section 2A.21c)==
+
The connection between the PSST posts and anchors varies based on the anchor gauge:
  
−
'''Support.''' It is suggested that district traffic personnel, in conjunction with construction and/or design personnel, conduct field checks of contract signing as soon as the roadway has been roughed-in to the extent that the actual visibility and effectiveness of each sign can be determined.
+
:* 12-gauge anchor – The connection between a 12-gauge anchor and the PSST post is accomplished using a corner bolt.  The corner bolt pulls the post into a corner of the anchor and eliminates any slack or play between the post and the anchor.
 +
:* 7-gauge anchor – The fit between a 7-gauge anchor and the PSST post is much looser and the radii of each do not match so a corner bolt will not eliminate the slack or play between these two devices.  Shoulder bolts installed at 90-degree angles corrects this issue; the shoulder of the bolt will pass through the holes in the 7-gauge anchor, but not through the holes in the post.  As a result, the two bolts push and lock the post in two directions making a solid connection.
 +
:* Add-on breakaway devices – when required/used, the manufacture’s recommendations and hardware (if supplied) need to be used to connect the anchor, breakaway and post together.
  
−
==903.2.18 Maintenance (MUTCD Section 2A.22)==
+
Breakaway aspects of PSST are a little more complicated compared to other MoDOT posts, the requirement for an add-on breakaway device heavily depends on the size and number of posts needed to support the sign. It is important to follow the guidance found in the signpost selection tools and MoDOT’s standard plans to determine when an add-on breakaway device is required and when it is not.  In applications where add-on breakaway devices are not required/used, PSST breaks away like a U-channel post in a yielding fashion, typically staying attached to the ground and lying down in front of the vehicle so the vehicle can pass over the assembly.  However, when an add-on breakaway device is used the breakaway function changes and the assembly is designed to break away from the ground and permit the vehicle to pass under the airborne assembly.
−
[[image:903.2.18 Maintenance.jpg|right|250px]]
 
−
'''Support.'''  The storing methods are in place to prevent damage to the sign sheeting.  Storing signs wet or horizontally will damage the retroreflective elements of the sheeting.  MoDOT has a warranty for the sign sheeting, but improper storage will void the warranty.  
 
  
−
'''Standard.'''  Should packaged signs become wet, they shall be unpacked immediately and allowed to dry.  Signs shall always be stored indoors on edge.  New signs shall be stored in a cool, dry area to prevent moisture damage.
+
'''Standard.'''  If PSST posts are used, they shall be either 2 in. or 2.5 in. 12-gauge posts.  The size and number of posts, as well as the requirement for add-on breakaway devices, shall be determined using the post selection tools.  PSST posts shall be installed in accordance with Standard Plans 903. <big>'''PSST posts installed on freeways, expressways, and ramps shall be installed using concrete footings.'''</big>
  
−
'''Guidance.''' All traffic signs should be kept properly positioned, clean, and legible, and should have adequate retroreflectivity.  Damaged or deteriorated signs should be replaced.
+
'''Guidance.''' District operations should be consulted to determine the most appropriate footing for PSST posts alongside other roadways as footing requirements vary based on soil conditions.
  
−
To assure adequate maintenance, a schedule for inspecting (both day and night) and replacing signs should be established. All employees whose duties require that they travel on the roadways should be encouraged to report any damaged, deteriorated, or obscured signs at the first opportunity.
+
===903.3.4.4 Pipe Posts===
 +
'''History.''' In 2022, a pipe post capacity evaluation was conducted that resulted in a change to the pipe post load capacity and pipe post inventory. Historically it was believed that pipe posts could support a sign size of up to 30 sq. ft. but the evaluation determined pipe posts could support a sign of up to 58.5 sq. ft. The evaluation also determined that the 3 sizes of pipe post being utilized were redundant. MoDOT historically used 2 ½ in., 3 in., and 4 in. pipe posts, however, the evaluation determined that the sign capacity of a post is determined by the breakaway assembly. The 2 ½ in. and 3 in. pipe posts used the same breakaway design and therefore the 3 in. pipe posts did not have any additional capacity over the 2 ½ in. post. As a result, the 3 in. post is redundant and was discontinued. This decision allows for a simplified inventory and eliminates confusion on pipe size. Maintenance can continue to utilize 3 in. pipe posts until the inventory is depleted but shall not order new 3 in. pipe posts. All existing 3 in. pipe posts shall be treated as 2 ½ in. posts for purposes of choosing posts using the post selection tables. 2 ½ in. pipe posts can be installed on existing 3 in. stubs.  
  
−
Weeds, trees, shrubbery, and construction, maintenance and utility materials and equipment should not obscure the face of any sign.
+
'''Support.''' MoDOT utilizes two sizes of pipe post, 2 ½ in. and 4 in. An important fact to understand is pipe post sizes are based on the inside diameter (I.D.) of the pipe post and not the outside diameter, this is the industry standard for pipe measurement. This is critical in selecting the correct pipe from inventory as well as charging out the correct post to keep your inventory levels correct.
  
−
A regular schedule of replacement of lighting elements for illuminated signs should be maintained.
+
Pipe posts have a similar sign capacity as PSST, even though they would appear to be able to carry a larger sign load due to size and thickness of the steel pipe. While the post themselves are far stronger than PSST, it is the breakaway of the pipe post which controls the sign load capacity of the post. The heavy-duty construction of a pipe post is not specifically related to sign load capacity but is more directly related to the durability of the post. Unlike PSST, which must be replaced after each vehicular impact, pipe posts are constructed with much thicker steel so the signpost can be impacted by a vehicle without being damaged and reinstalled for continued use. There are many pipe posts on our right of way that have been there for two or three generations of signs and are still functional so while they are heavier and more expensive, they are a long term investment and are far more durable.
−
 
−
{| style="margin: 1em auto 1em auto"
 
−
|-
 
−
|[[image:903.2.18 Flat Sign Storage.jpg|left|175px|thumb|<center>'''Flat sign storage'''</center>]]
 
−
||[[image:903.2.18 Large Sign Storage.jpg|175px|left|thumb|<center>'''Large sign storage'''</center>]]
 
−
|}
 
  
−
==903.2.19 Sign Inspection and Inventory (MUTCD Section 2A.22a)==
+
Pipe posts are used for single and double signpost assemblies to support signs up to 58.5 sq.ft. These posts are typically used on freeways and expressways where signs are larger, wind speeds can be higher due to more open right of way and the sign may see larger snow load impact from plows pushing more snow from across multiple lanes to the right side of the roadway.  
  
−
'''Standard.'''  A sign maintenance program shall be established for all routes within our systems. All signs on all routes shall be inspected once a year as follows:
+
Pipe posts are also the preferred post to support large route assemblies, especially on freeways and expressways. In the past, Wide Flange posts were once used to support these assemblies (and many remain in place) as the design of the post was well suited to attaching a series of backing bars needed to support the assemblies. However, the multi-direction breakaway and high resistance to torsional or twisting forces makes pipe posts the preferred post over the Wide Flange design.
  
−
A. Even numbered years a daylight inspection shall be performed.
+
Pipe posts are designed and fabricated with the breakaway device as part of the post / stub combination; as long as the post and stub breakaway is assembled correctly the post is capable of being impacted from any direction. Details for the assembly of this post system are found in Standard Plans 903, special attention must be paid to the placement of three breakaway bolts, the required and proper placement of all washers within the breakaway and most critically to the proper tightening and torque of the breakaway bolts.
  
−
B. Odd numbered years a night inspection shall be performed.
+
'''Standard.''' If Pipe posts are used, they shall be either 2 ½ in. or 4 in. in size. The size and number of posts shall be determined using the post selection tools. Pipe posts shall be installed in accordance with Standard Plans 903.
  
−
District database information containing sign logs for interstate, primary and supplementary systems shall be submitted to Maintenance office by July 1 of each year.  It is the intention for this Division office to retain only the current year's sign logs.  Each district shall retain copies of previous sign logs.  The sign logs sent to the Traffic Division as required by the due date list shall be copies of each district's sign logs with the district retaining the master and a backup.
+
===903.3.4.5 Wide Flange (I-Beam) Posts ===
 +
'''Support.''' MoDOT uses 6 sizes of Wide Flange posts, commonly referred to as Design #1, #2, #3, #4, #5 and #6, increasing in size and capacity respectively.  Wide Flange posts are typically used to support signs 30 ft2 and larger and are MoDOT’s highest capacity ground-mount sign support.  As with Pipe Posts, Wide Flange post are designed to be a more durable post intended to last multiple generations of signs and designed to be able to be impacted by vehicle and then reassembled and reused.
  
−
'''Guidance.''' Appropriate district personnel should perform the inspection of the interstate and primary systems.  The sign inventory process is typically:
+
Wide Flange post are designed and used to support large structural signs, signs made using extruded aluminum panels instead of flat sheet aluminum.  The cross section of a wide flange post being that of an I-beam permits structure signs to be easily attached to the post using post clips or “dog clamps” instead of using traditional sign bolts.  These posts are traditionally used on freeways and expressways only; however, there may be special applications where they may be used on two lane roadways if the size of the sign is too large for other post options.
  
−
A. The sign inspection log shall include every sign on all routes within our system.
+
Wide Flange posts were once the standard to support large route assemblies on freeways and expressways, however, over time two weaknesses were identified that changed this direction, making Pipe posts the better option. The two weaknesses of Wide Flange posts used to support route assemblies are:
  
−
B.  The exact message of those signs classified as guide signs shall be provided on the sign inspection log with no abbreviations.
+
:* Safety - Route assemblies many times are installed in and around intersections and in these locations it is theoretically possible some assemblies could be impacted from any direction of travel.  Single Wide Flange posts are only breakaway in two directions and are not designed to be breakaway if impacted on either side, just the front and back of the sign.  Pipe posts are designed as a multi-breakaway post and can be impacted from any direction making them the better option for these installations. 
 +
:* Torsional / Twisting Force Resistance – Although Wide Flange posts are very strong, they do have a limited resistance to twisting moments when installed as a single post installation.  In wind prone locations, sign assemblies on a single Wide Flange post can begin to twist in the wind, and if this continues long enough, it can cause the post to fatigue and break off at the base.  Pipe posts have an extreme resistance to twisting and can resist much larger torsional forces compared to wide flange posts.
  
−
C.  Signs other than guide signs may be abbreviated. Care should be used in abbreviations that there will be no misunderstanding as to their meaning.
+
As with Pipe Posts, Wide Flange posts are fabricated with the breakaway system as part of the post / stub assembly.  While Wide Flange posts have a breakaway assembly at ground level like Pipe posts, they also require a hinge system located directly below the sign.  The hinge system permits the wide flange post (the portion from the ground to the bottom of the sign) to swing up out of the way of a vehicle when impacted without the upper portion of the post and the sign needing to move. This reduces the mass that a vehicle must move when it impacts the post and in return reduces the impact energy to the car.
  
−
D.  For those signs within an assembly, such as a junction assembly, the log should reflect the total number of signs within that assembly.
+
Unlike all other MoDOT posts, there are minimum post spacing which must be taken into consideration when selecting the correct number and size of post.  Wide Flange Posts are much heavier than any other MoDOT post and hitting two of these posts at the same time in most cases would impart too much energy to the vehicle and would not meet minimum breakaway standards.  These special considerations are included in Standard Plans 903 which contains all of the fabrication and installation details for Wide Flange Posts, however, due to their critical nature they are also listed here:
  
−
E. Trailblazer signs for LOGO signs should be logged using the corresponding generic service panel (i.e.: Gas LOGO D9-7G, Food LOGO D9-7F, Lodging LOGO D9-7L, Camping LOGO D9-3, Attractions LOGO D9-7a).
+
:* Wide Flange Post Designs #1 and #2 have no minimum post spacing requirements.
 +
:* Wide Flange Post Designs #1 or #2 shall not be installed in three post configurations supporting signs less than 11 feet width.  
  
−
F. Signs requiring maintenance should be noted on the log.  
+
:* Wide Flange Post Designs #3, #4, #5 and #6 shall be spaced at least 7 ft. apart.
  
−
Sign inspections should be performed and recorded as follows:  
+
The post selection tool is designed to utilize two post installations over three post installations to help address minimum post spacing; it also reduces the number of footings which need to be constructed.  However, there are some general rules based on sign size used to judge the number post for different size ranges of signs:
  
−
A. All signs should be logged if the sign’s face is visible for that direction of travel.
+
:* Signs between 6 ft. and 17 ft. wide will typically be supported on two posts
 +
:* Signs wider than 17 ft. will typically be supported by three posts
 +
:* Signs of any size are not recommended to be installed on one Wide Flange post
  
−
B.  When a sign on an intersecting road with our system is logged, the other system should be identified.
+
'''Standard.''' If Wide Flange posts are used, they shall be either a structural #1, #2, #3, #4, #5 or #6 in design.  The size and number of posts shall be determined using the post selection tools.  Wide Flange posts shall be installed in accordance with Standard Plans 903.
  
−
:1.   If possible, identify the [http://www.modot.org/newsandinfo/CountyMaps.htm county road] or city street by name and also note whether the intersecting road is a crossroad or on the right or left.
+
==903.3.5 Secondary Sign Supports – Post Extensions==
 +
'''Support.''' These supports are 3 in. aluminum I-Beam used to attach exit number panels to the top of, or to hang a secondary sign below, structural signs on new installations. Details of these posts are shown in the Standard Plans 903.
  
−
:2. This data can be noted in parenthesis in the comments section.
+
'''Option.'''  There are occasions where modifications and/or additions must be made to existing sign installations where the existing posts are not long enough to support the new sign assembly.  In these cases, it is permissible to utilize secondary sign supports to effectively extend the primary signposts to support signs a maximum of 3 feet taller than the existing primary signposts.
  
−
:3. Other items which should be noted in the comments section are whether the signs are mounted back-to-back and/or at 90 degrees to another sign.  
+
Secondary sign supports may only be used to allow taller signs to be installed on existing signposts if the signposts have the capacity to carry the larger sign based on signpost selection tools.
  
−
C.  Slashes should be used to differentiate between lines on a sign.
+
If a new sign assembly is more than 3 ft taller than the existing primary signposts, new signposts shall be installed.
  
−
D.  Arrows should be recorded as follows AH (ahead), LT (left), RT (right), 45LT and 45RT.
+
==903.3.6 Backing Bars==
 +
'''Support.''' Backing bars are typically used to support and stiffen wide flat sheet signs mounted on single signpost or to help support the individual signs which make up sign assemblies to form one unified sign assembly.  Details for backing bars can be found in Standard Plans 903.  
  
−
E.  Routes must be designated with a prefix in order to efficiently sort the file.
+
==903.3.7 Breakaway Assemblies==
 +
'''Standard.''' All signposts installed on right of way shall meet federal breakaway standards and MoDOT standards.  Signposts not meeting current standards, but met the standards at the time of their installation, may remain in place until the end of their service life.
  
−
:1.  The designation of "IS" will be used for Interstate Routes, "US" for U.S. Routes, "MO" for Missouri lettered and numbered routes and “BU” for Business Routes.
+
Sign trusses and other large sign support structures that are not breakaway shall be protected by acceptable shielding, such as guard rail or barrier wall.  
  
−
:2. Lettered prefixes will immediately precede the route designation with no space or dash between the designation and the route.
+
'''Support.'''  4 in. x 4 in. wood posts do not need any modification to be breakaway, however 4 in. x 6 in. and 6 in. x 6 in. wood posts will need to be cross drilled to meet breakaway standards.  U-Channel posts do not require breakaway modifications if they are direct driven into the ground, however, if the ground stub and slice installation method is used the installation will need to be installed according to the Standard Plans 903 to meet breakaway requirements.  PSST will require breakaway devices added in certain applications based on sign and number of posts used for an installation.  The signpost selection tools will indicate when a breakaway is required for PSST posts.  Pipe and Wide Flange posts have the breakaway devices integrated into the post design.  
  
−
:3. When the route is a business or spur route, no designation will be necessary.  
+
==903.3.8 Sign Orientation (MUTCD Section 2A.20)==
 +
'''Support.''' The orientation of the face of a sign in relation to the driver and roadway is critical to visibility and legibility, especially at night.  The effectiveness of the retroreflective sheeting on a sign can be negatively impacted if the orientation of the sign face is not correct, due to incorrect installation and/or a signpost being damaged and knocked out of alignment.
  
−
F.  Signs within an assembly should be numbered from top to bottom and the columns will be lettered from left to right with the first column having no letter, the second column having letter "A" and so on. (See Figure 903.2.21 Standard Assembly Numbering for Route Marker Assemblies)
+
The orientation of a sign can also help reduce unwanted reflection or glare off of the sign face.  The skew angle, shown in Standard Plans 903, is designed to help address this glare issue for tangent sections.  
  
−
G. The log mile used to record the location of a sign should be the same as the log mile system established for accident data.  
+
'''Guidance.''' Unless otherwise provided in the EPG, signs should be vertically mounted at approximately right angles to the direction of, and facing, the traffic that they are intended to serve, with an approximate 3 degree skew angle away from traffic.  
  
−
It is recommended an individual should be trained for proper mounting location and sign height, as well as inventory and sign ordering procedures.  This individual would check to see that items marked on sign logs are accomplished within the year.  The number of individuals trained in signing is based on district needs.
+
Signs that are placed 30 ft. or more from the pavement edge should have a skew angle that is turned toward the road to improve the effectiveness of the retroreflective sheeting.  
−
 
 
−
Sign quantities should be indicated by commodity code for each sign number within each organization.  This is imperative to enable the inventory to be correctly maintained.
 
−
 
 
−
'''Support.'''  The maximum inventory levels for all signs have been determined from the average annual usage for each type of sign.  The maximum inventory represents approximately 1/3 of the average annual usage.  This policy does not apply to signs used for emergency closures and routine maintenance operation traffic control signs.
 
−
 
 
−
The route designations used during the log process allow the records to be sorted by route without sorting out additional routes.  For example, when sorting Route 3 without the designation prior to the number, one would also access Routes 35, 350 etc.
 
−
 
 
−
Examples of the lettered prefixes for route designations would be as follows:
 
−
 
 
−
{| border="1" class="wikitable" style="margin: 1em auto 1em auto"
 
−
|+
 
−
! style="background:#BEBEBE"|Type !! style="background:#BEBEBE"|Route
 
−
|-
 
−
| align="center"|IS|| align="center"|435
 
−
|-
 
−
| align="center"|US|| align="center"|40
 
−
|-
 
−
| align="center"|MO|| align="center"|15
 
−
|-
 
−
| align="center"|RT|| align="center"| AA
 
−
|}
 
−
 
 
−
When the route is a business or spur route, no designation will be necessary. The nomenclature would be as follows:
 
−
 
−
{| border="1" class="wikitable" style="margin: 1em auto 1em auto"
 
−
|+
 
−
! style="background:#BEBEBE"|Type !! style="background:#BEBEBE"|Route
 
−
|-
 
−
| align="center"|BU|| align="center"|60
 
−
|-
 
−
| align="center"|SP|| align="center"|5
 
−
|}
 
−
 
 
−
==903.2.20 Salvaged Signs (MUTCD Section 2A.22b)==
 
−
 
 
−
'''Standard.'''  All damaged aluminum signs, except for those that are severely mangled or bent, should be kept for reclamation.  All aluminum signs that are reclaimable shall be delivered to Moberly Correctional Facility at Moberly, Missouri.
 
−
 
 
−
All steel signs shall be kept at the district and sold as scrap by the district.  Before a steel sign is sold for scrap the sign face shall be defaced so that the sign can no longer be used.
 
−
 
 
−
'''Guidance.'''  Signs should be delivered on normal workdays between the hours of 8:00 a.m. and 2:30 p.m.  One day's notice of delivery should be given by calling the institution's clerk at (660) 263-3778, Ext. 442.
 
−
 
 
−
'''Support.'''  All signs are the property of the Commission with the exception of TODS and signs installed by others.  Proper procedures need to be followed for disposing and defacing of old, faded or damaged signs.  We are not allowed to sell signs.
 
−
 
 
−
The Moberly Correctional Facility does not require signs to be banded or on pallets. 
 
−
 
 
−
There are several available options of hauling these reclaimable signs to the Moberly facility.  One option is to use district resources to haul these signs.  Another option is to use the current contract carrier who is hauling signs to your location from the sign shop; or if General Services is hauling to your location you may use them.
 
−
 
 
−
The last two options of delivery systems will have certain restrictions for hauling of this product.  Contact the service provider to ensure that you meet the requirements.
 
−
 
 
−
==903.2.21 Response to Emergencies (MUTCD Section 2A.22c)==
 
−
 
 
−
'''Support.'''  Risk Management has established guidelines concerning the response to replacing signs that have been knocked down or otherwise lost, see Table 903.2.22. 
 
−
 
 
−
'''Guidance.'''  The Risk Management Manual should be consulted for the proper procedures to follow.
 
−
 
 
−
==903.2.22 Median Opening Treatments for Divided Highways with Wide Medians (MUTCD Section 2A.23)==
 
−
 
 
−
'''Guidance.'''  Where divided highways are separated by median widths at the median opening itself of 30 ft. or more, median openings should be signed as two separate intersections.
 
−
 
 
−
[[image:Figure 903.2.22.gif|frame|center|thumb|'''Figure 903.2.22. Standard Numbering for Route Marker Assemblies''']]
 
−
 
 
−
 
 
−
====<center>''Table 903.2.22 Incident Response Plan - Signing''</center>====
 
−
 
 
−
{| border="1" class="wikitable" style="margin: 1em auto 1em auto"
 
−
|+
 
−
!  !! style="background:#BEBEBE"|PRIORITY 1 !! style="background:#BEBEBE"|PRIORITY 2 !! style="background:#BEBEBE"|PRIORITY 3 !! style="background:#BEBEBE"|PRIORITY 4
 
−
|-
 
−
! style="background:#BEBEBE"|PRIORITIES ARE GUIDELINES AND MAY BE UPGRADED IF PRIMARY CONTACT DEEMS NECESSARY !!Urgent. Respond as soon as possible (day or night, weekends, or holidays) suspending other lower priority work if necessary. May represent immediate hazard to the public.!!Repair should be accomplished as soon as practical during normal working hours, but only after Priority 1 repairs are completed.!!Repair should be accomplished with higher urgency than routine maintenance.!!Not urgent. Normally considered routine maintenance.
 
−
|-
 
−
| LANE CLOSURE NOTIFICATION/ APPROVAL REQUIRED ** || NO || NO ||YES||YES
 
−
|-
 
−
!style="background:#BEBEBE"|SIGNING!! - !!-  !!-  !! -
 
−
|-
 
−
|BARRICADES (Permanent)
 
−
| -  || X ||- ||-
 
−
|-
 
−
|DAMAGED OR MISSING ROADSIDE DELINEATORS
 
−
| - ||-||- ||X
 
−
|-
 
−
|EXPRESSWAY/FREEWAY SIGNS *
 
−
| - ||X ||- ||-
 
−
|-
 
−
|GUIDE SIGNS *
 
−
| -  ||-  ||X||-
 
−
|-
 
−
|INFORMATION SIGNS *
 
−
| - ||- ||X ||-
 
−
|-
 
−
|REGULATORY SIGNS *
 
−
|Critical, i.e.; Stop, Yield, Do Not Enter, Wrong Way, One Way||All Others ||- ||-
 
−
|-
 
−
|SCHOOL SIGNS *
 
−
| - ||- || X ||-
 
−
|-
 
−
|SIGN LIGHTING MALFUNCTION
 
−
| - ||- ||X ||-
 
−
|-
 
−
|SIGN TRUSS STRUCTURE DAMAGE
 
−
|Creating a Traffic Hazard||- ||Not a Traffic Hazard|| -
 
−
|-
 
−
|VISIBILITY(Weeds, Trees, etc.)
 
−
|Involving Regulatory Signs or Signals||All Others||- ||-
 
−
|-
 
−
|WARNING SIGNS *
 
−
| - ||X   ||- || -
 
−
|-
 
−
| colspan="5"|* Damage that makes the sign ineffective.
 
−
|-
 
−
| colspan="5"|** NHS Routes and all Other Routes With AADT of 1700 or Greater
 
−
|}
 
−
 
−
[[image:903.2.22.jpg|center|820px]]
 
  
 +
'''Option.''' While the standard skew angle is 93 degrees, the skew angle may be adjusted to maintain brightness and avoid glare for signs on curved sections of road. On roadways with significant grades, sign faces may be tilted forward or back from vertical position to improve the viewing angle.
  
 +
==903.3.9 Sign Mountings (MUTCD Section 2A.21)==
 +
'''Support.'''  Attaching a sign properly to a sign support is critical in order to properly orient the sign in relation to the driver as well as provide a durable, long life installation.
 +
 +
'''Standard.'''  Plastic/nylon washers shall be used between the heads of all twist fasteners (such as screws, bolts or nuts) and the sign face to protect the sheeting from the twisting action of the fasteners. 
  
 +
Signs shall be attached to each type of sign support in accordance with Standard Plans 903.
  
  
  
−
[[Category:903 Highway Signing|903.02]]
+
[[Category:903 Highway Signing|903.03]]

Latest revision as of 12:32, 28 March 2024

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903.3.1 Ground-Mounted Sign Installation

Forms
Signpost Selection Guide
Printable Signpost Selection Guide for use in the field

Guidance. Signs should be ground-mounted whenever possible unless mounting overhead is justified or required.

Standard. If signs are placed on existing supports, they shall meet other placement criteria contained in this article.

Utility and light poles shall not be used to mount signs as they are either not the property and maintenance responsibility of MoDOT or are not designed to carry the additional wind loading a sign adds to the structure.

Option. In areas with space restrictions, available sign truss columns, signal poles, bridge columns, or other significant MoDOT structures, excluding roadway lighting structures, may be used to mount flat sheet aluminum signs.

903.3.2 Lateral Offset (MUTCD Section 2A.19)

Support. The minimum lateral offset is intended to keep trucks and cars that use the shoulders from striking the signs or supports, while keeping signs and object markers close enough to the roadway to be effective.

Standard. Ground-mounted sign supports shall be crashworthy and meet the latest federal crash standards at the time of installation.

Guidance. The provisions below should be applied unless specifically stated otherwise in the EPG for a particular sign or object marker. For ground-mounted signs, the minimum lateral offset should be 12 ft. from the edge of the travelway. If an existing shoulder is wider than 6 ft., the minimum lateral offset for ground-mounted signs should be 6 ft. from the edge of the shoulder or front face of curb. See Figures 903.2.18.1 and 903.2.18.2 which illustrate typical examples of the lateral offset requirements contained in this portion of the article.

Maximum offset will depend on roadway geometrics, profiles, and cross-sections, which all affect the visibility of the sign. Signs are generally to be placed no more than 15 ft. from the edge of shoulder.

Ground-mounted signs placed in a gore only requires a minimum of 2 ft. lateral offset from edges of shoulder, face of barrier walls or guard rail.

For divisional and channelizing islands, a 2 ft. lateral offset should be maintained between the edge of sign and the front face of curb. For islands with restricted width the sign should not extend beyond the curb face.

Option. Deviation from the standard lateral offset may be used if a signs effectiveness and visibility are maintained to account for variations in roadside features. For example, to avoid placing signposts in the flow line of a ditch, avoiding drainage structures, pull boxes or sidewalks.

Option. Lesser lateral offsets may be used in business, commercial or residential areas where limited space is available to place signs due to limited right of way, sidewalks or other restrictions which keep the sign from being installed at the correct offset. In these cases, the edge of the sign may be placed up to, but not beyond the face of the curb making every effort to maximize the offset with the space available.

Guidance. Ground-mounted sign supports should not intrude into the usable width of a sidewalk or other pedestrian facility.

903.3.3 Mounting Height (MUTCD Section 2A.18)

Support. Installing signs at the proper mounting height is critical not only for the sign to be seen and function, but also to the functionality of the breakaway design for each type of signpost. Mounting heights are typically listed as “nominal” as it is critical to keep the signs a minimum distance above the ground, however, signs installed excessively high also have issues, such as:

  • Place signs outside of the drivers line of sight
  • Place signs outside the effective range of vehicle headlights at night making signs less visible
  • Signs mounted too tall are more susceptible to wind resulting in signs being pushed out of plumb or being blown over

903.3.3.1 Mounting Height – U-Channel, Wood, Perforated Square Steel Tube (PSST), Pipe Posts and 4 in. Square Steel Posts (MUTCD Section 2A.18)

Support. There are typically two mounting heights for signs on u-channel, wood, PSST, pipe posts and 4 in. square steel posts, 5 feet and 7 feet. Traditionally, the 5-foot mounting height has been applied to “rural” areas and the 7-foot mounting high applied to “urban” areas or within incorporated city limits. However, the term “urban” has more to do with the conditions the signs are being installed within and less about being located within an incorporated city limit. The purpose of the 7-foot mounting height is to provide clearance for passing bicycle and pedestrian traffic, making the sign more visible over parked vehicles along the roadway and permits improved sight distance to drivers permitting them to see below the sign.

The 7-foot mounting height also applies to all freeway and expressway applications to enhance long distance visibility.

Standard. Standard Plans 903 shall be referenced for specific installation and mounting height details. The details in Standard Plans 903 and EPG 903.3 Ground-Mounted Sign Supports shall apply to all signs unless specifically stated otherwise for a specific sign or object marker elsewhere in the EPG.

The minimum mounting height of a sign shall be measured vertically from the bottom of the sign to the elevation of the near edge of the pavement. Minimum sign mounting heights shall be as follows:

  • Sign located in rural areas – 5 feet,
  • Sign located in urban areas – 7 feet,
  • Signs located on freeways and expressways – 7 feet.

The length of post measured from the bottom of the sign to the ground shall also be a minimum of 5 feet. If the length of any post within a sign assembly measures less than 5 feet from the bottom of the sign to the ground, the minimum sign mounting height shall be increased to achieve the minimum 5-foot post length.

Option. Signs may be installed at 5 feet within the boundaries of incorporated city limits if the all following conditions apply:

  • The sign is located outside of business, commercial or residential areas where there are no high densities of entrances and cross street intersections
  • There is no on street parking
  • There are no sidewalks with bicycle or pedestrian traffic

If a secondary sign is mounted below the primary sign on the same signpost(s), the mounting height for the assembly, measured from the near edge of the pavement to the bottom of the secondary sign, may be 1 foot lower than the minimums listed above.

In cases where signs are located on steep back slopes, it may be advantageous to relocate the sign forward or back from the proposed location to an area that is flatter to avoid a sign being mounted too high.

Guidance. Signs located outside of incorporated city limits that are located in areas having characteristics of an urban area, such as around businesses, heavy residential areas, areas with on street parking and areas with sidewalks which support bicycle and pedestrian traffic, should be installed at 7 feet.

Route marking assemblies consisting of a route sign and auxiliary signs should be treated as a single sign for the purposes of sign mounting height.

Support. Fig. 903.2.18.1 illustrates typical examples of the mounting height requirements contained for signs installed on U-Channel, Wood, PSST and Pipe Posts.

903.3.3.2 Mounting Height – Wide Flange (I-Beam) Posts (MUTCD Section 2A.18)

Support. Installing signs at the proper mounting height is critical not only for the sign to be seen and function, but also to the functionality of the breakaway design. Proper mounting height is more critical for breakaway function on Wide Flange posts compared to all other posts due to the hinge component of this post design. As with the other post types, mounting heights for Wide Flange posts are listed as “nominal” as excessive mounting heights have the same negative effects for these installations as exists with the other post types. Wide Flange post mounting heights are greater than other posts, so in areas with back slopes it is recommended to seek out a flatter location in advance or downstream of the original installation to keep the sign as low as possible.

Minimum mounting heights for Wide Flange post installations are not related to rural or urban classifications, but are directly related to how the breakaway system functions. Standard Plans 903 provides details on the nominal mounting heights on wide flange posts. Key details to focus on are:

  • No wide flange post can be shorter than 7’ 9” measured from the hinge to the top of the stub.
  • The hinge point is always below the lowest sign which is attached to the wide flange post.
  • Nominal mounting heights vary depending if there is one sign mounted on the posts or two.
  • For signs located in areas of back slopes, the minimum mounting height may have to be increased, or the sign installed in a different location, in order to achieve the minimum post length of 7ft. 9 in.

903.3.4 Ground-Mounted Sign Support Selection

Support. The majority of MoDOT signs are installed and supported on one of 5 types of ground-mounted sign supports or signposts. The selection of signpost is based on many factors, but primarily on the size of sign being installed and the type of roadway the sign is being installed along. There is some overlap in signpost applications; more than one signpost may be applicable to a given installation. The final selection of the post type is based on the attributes needed for a support as discussed in each classification of signpost below.

The number of posts needed to support a sign is primarily based on the width of a sign. Typically, signs 48 inches wide and wider are installed on two or more posts. This requirement is based on two factors, the capacity of the post and the long-term stability of the assembly. A wide sign installed on one post will place a torsional force onto a post and in windy conditions can result in an assembly not staying plumb and, in some cases, an actual failure of the post itself.

Standard. The selection of the proper size of signpost shall be based on the Signpost Selection Guide listed above. These tools will specify if a post type has the capability to support the sign in question and then specify what size post is required based on the requirements of the installation. Before the correct size of PSST or Wide Flange post can be selected, the length of the longest post must first be determined. To determine this, the offset and mounting height must first be determined.

903.3.4.1 U-Channel Posts

Support. MoDOT utilizes two primary sizes of U-Channel Posts, a 3 lb/ft high carbon, rerolled rail steel post for sign installations and a low carbon steel 1 lb/ft post for road side delineation.

U-channel posts can be used to support MoDOT’s small signs, such as no parking signs, object markers and chevrons on two lane roadways. U-channel posts are typically not suited to support larger permanent signs as they have limited torsional rigidity and have less ability to hold a larger sign steady in windy conditions. These are typically the most economical posts to use to support smaller signs and given these types of signs tend to be installed closer to the roadway their ability to yield more easily to impacts means they pose less of a damage risk to vehicles. U-channel posts are typically installed by driving the post into the ground without a stub or anchor, however, there is a stub / post installation option available which is detailed in the standard plans.

U-Channel posts are considered breakaway with no additional breakaway devices needing to be added. While there are breakaway devices available for U-channel posts, MoDOT’s use of this type of post for smaller signs typically doesn’t justify their use. A U-channel post’s breakaway is typically a yielding function, meaning as a vehicle impacts the assembly, the post yields and lies down in front of the vehicle so it can pass over the assembly.

Standard. U-channel posts shall be installed in accordance with the details found in Standard Plans 903. Signpost selection tools shall be used to determine sign sizes U-channel posts can support and the number of posts needed.

903.3.4.2 Wood Posts

Support. MoDOT’s specs permit three sizes of wood posts to be used: 4 in. x 4 in., 4 in. x 6 in., or 6 in. x 6 in. MoDOT’s wood posts are pressure treated to promote longer life and resist rot and insect damage. Wood posts were once MoDOT’s primary post to support signs on two lane roadways; however, due to issues with material stability PSST posts have become MoDOT’s standard post.

When used, wood posts are capable of supporting most sign assemblies on two lane roadways, from route marker assemblies, speed limit signs, warning signs and distance and destination signs. The use of a high quality wood post and proper installation is the key to a successful installation.

Guidance. The continued use should take into consideration the special characteristics listed in EPG 903.3 Ground-Mounted Sign Supports.

Proper installation is also critical for the stability of the sign assembly. The wood post should be placed a minimum of 36 inches into the ground, deeper for larger signs or in areas where the soil is weak or sandy, to keep the signpost plumb. When backfilling the hole, material should be added in lifts, or levels, in order to properly compact the backfill. Loose or fine materials, such as sand, sandy soil or dry concrete mix typically will not provide a long term solid backfill and can result in the post falling out of plumb over time.

MoDOT’s specifications should be followed when purchasing wood signposts. These specifications address a posts load capacity, breakaway attributes and the compatibility between the pressure treatment chemicals and our aluminum signs and sign hardware.

Option. While the soil originally removed from the hole can be used to back fill around the post other alternatives may be used, such as smaller quarry rock with the crushing fines mixed in, concreted mix or expanding polyurethane foam.

Support. Wood posts are considered breakaway without an add-on breakaway device; however, some sizes of post do need special preparation. 4 in. x 4 in. wood post are considered breakaway without any special modifications; however, 4 in. x 6 in. and 6 in. x 6 in. posts must be cross drilled at the base to weaken them so they will break away. The size of the holes and where they are drilled is critical to these posts meeting breakaway requirements. The details for these holes are found in the Standard Plans 903, it is important to note these breakaway holes are drilled in the sides of the post, not in the front of the post where the sign is mounted.

Standard. If wood posts are used, the proper size and number of posts shall be determined by using the post selection tools.

Fig. 903.3.4.2, Details for Wood Posts Requiring Breakaway Design

History. One of the earliest issues experienced with wood posts is their tendency to warp and twist, both before and after installation. Keeping a sign plumb and appropriately oriented to the roadway is critical to maintain the sign’s legibility and night time retroreflectivity performance. This aspect of wood posts resulted in significant waste of inventory when the posts warped and twisted before being used and increased work load on signing crews who had to correct warped and twisted posts after installations. Another concern with the use of wood posts was the installation required a hole to be dug, the posts set and property back filled so the sign would remain upright. If soil conditions prohibited a hole being dug deep enough or the back fill not capable for being compacted sufficiently the assembly would fall out of plumb. Along with these installation aspects, a wood post sign assembly can be very heavy, especially when the pressure treated wood is still wet with the pressure treating fluids and this can result in the need for additional people to set the post and/or increased risk of injury setting the post by hand.

Towards the end of MoDOT’s reliance on wood posts a new issue was identified relating to the more environmentally friendly treatment process called ACQ (Ammoniacal Copper Quaternary). ACQ replaced CCA (Chromated Copper Arsenate) for residential applications as CCA had chemical component which were not recommended for routine contact with skin. However, unlike CCA, ACQ (especially early versions) turned out to be very corrosive to metals, especially to aluminum. This corrosive nature requires special fasteners to resist this corrosive effect. Early applications of ACQ in other states realized serious sign corrosion to the point the sign would fall off the post in a matter of a few years. While it appears this has improved, special fasteners with special protective coatings are still recommended for use with ACQ posts. As a result, ACQ posts do not meet MoDOT’s specifications and should not be used to support signs. CCA treated posts are still MoDOT’s standard for wood posts, however, it is not commonly available at local home improvement centers and at many lumber yards. Due to MoDOT’s limited use of this product contract purchasing typically is not economical or possible.

903.3.4.3 Perforated Square Steel Tube Posts (PSST)

Support. MoDOT utilizes two sizes of PSST posts, 2 in. and 2.5 in., both being made from 12-gauge steel. PSST became MoDOT’s standard post for most sign installation applications on two lane roadways in the early 2000’s, replacing wood posts. PSST usage has since expanded to some applications on freeways and expressways.

Unlike U-channel or Wood posts, PSST utilizes a ground anchor, or footing, within which the post is then placed. MoDOT has several options in its specifications with respect to ground anchor/foundation systems, the use of each option is heavily based on the soil condition.

The anchor/footing types for PSST are:

  • 12-Gauge PSST Anchor – this is the basic direct-driven anchor for 2 in. PSST posts. A 12-gauge anchor does not exist for 2.5 in. PSST posts.
  • 7-Gauge Anchor – this is a heavy wall box tube anchor which is the basic direct-driven anchor for 2.5 in. PSST posts. It is also an optional heavy anchor for 2 in. PSST posts in rocky ground where a 12-gauge anchor may deform when driven. The 7-gauge anchor is also the anchor that must be used when installing a concrete or polyurethane footing.
  • Omnidirectional, or stabilization, Anchor – this is the appropriate 12-gauge or 7-gauge direct-driven anchor with 4 soil stabilization plates added to the anchor to increase soil surface area to help keep signs plumb in weaker soils and/or in windy areas. A JSP will be needed to specify this anchor type on a project.
  • Concrete Footings – In some applications it may be desired to install a concrete footing for PSST, similar to the footings for Pipe Post or Wide Flange Post. Concrete footings provide a stronger foundation compared to the directly-driven anchors listed above. A concrete footing may also be required in cases where the ground is too hard or rocky to direct drive the anchor and a hole may need to be dug in order to install the anchor. All concrete footing installations use a 7-gauge anchor (that only has holes at the top of the tube) because concrete would flow through the holes of a normal 12-gauge PSST anchor.
  • Polyurethane Foam Footings – This is an alternate to a concrete footing for PSST post installations. This permits the footing and the sign to be installed in one trip compared to concrete, which requires a second trip to allow the concrete to cure. The installation requirements for an expanding foam footing are the same as a concrete footing except for the diameter of the footing, which is smaller. It is important to make sure the expanding foam used meets MoDOT specifications as not all foam products are acceptable to support a breakaway sign.
POST AND ANCHOR DATA TABLE
POST ANCHOR BREAKAWAY REQUIRED
NUMBER OF POSTS
GAUGE SIZE GAUGE DIMENSIONS 1 2 3
12 2" x 2" 12 2.25" x 2.25" x 36" NO NO YES
7* 2.5" x 2.5" x 36" NO NO YES
12 2.5" x 2.5" 7 3 x 3 x 36" NO YES YES
12 (2.5"x2.5")+(2.25"x2.25") 7 3 x 3 x 36" YES YES YES
* TO BE USED WITH CONCRETE FOOTINGS OR IS AN OPTION IN ROCKY SOIL CONDITIONS

The connection between the PSST posts and anchors varies based on the anchor gauge:

  • 12-gauge anchor – The connection between a 12-gauge anchor and the PSST post is accomplished using a corner bolt. The corner bolt pulls the post into a corner of the anchor and eliminates any slack or play between the post and the anchor.
  • 7-gauge anchor – The fit between a 7-gauge anchor and the PSST post is much looser and the radii of each do not match so a corner bolt will not eliminate the slack or play between these two devices. Shoulder bolts installed at 90-degree angles corrects this issue; the shoulder of the bolt will pass through the holes in the 7-gauge anchor, but not through the holes in the post. As a result, the two bolts push and lock the post in two directions making a solid connection.
  • Add-on breakaway devices – when required/used, the manufacture’s recommendations and hardware (if supplied) need to be used to connect the anchor, breakaway and post together.

Breakaway aspects of PSST are a little more complicated compared to other MoDOT posts, the requirement for an add-on breakaway device heavily depends on the size and number of posts needed to support the sign. It is important to follow the guidance found in the signpost selection tools and MoDOT’s standard plans to determine when an add-on breakaway device is required and when it is not. In applications where add-on breakaway devices are not required/used, PSST breaks away like a U-channel post in a yielding fashion, typically staying attached to the ground and lying down in front of the vehicle so the vehicle can pass over the assembly. However, when an add-on breakaway device is used the breakaway function changes and the assembly is designed to break away from the ground and permit the vehicle to pass under the airborne assembly.

Standard. If PSST posts are used, they shall be either 2 in. or 2.5 in. 12-gauge posts. The size and number of posts, as well as the requirement for add-on breakaway devices, shall be determined using the post selection tools. PSST posts shall be installed in accordance with Standard Plans 903. PSST posts installed on freeways, expressways, and ramps shall be installed using concrete footings.

Guidance. District operations should be consulted to determine the most appropriate footing for PSST posts alongside other roadways as footing requirements vary based on soil conditions.

903.3.4.4 Pipe Posts

History. In 2022, a pipe post capacity evaluation was conducted that resulted in a change to the pipe post load capacity and pipe post inventory. Historically it was believed that pipe posts could support a sign size of up to 30 sq. ft. but the evaluation determined pipe posts could support a sign of up to 58.5 sq. ft. The evaluation also determined that the 3 sizes of pipe post being utilized were redundant. MoDOT historically used 2 ½ in., 3 in., and 4 in. pipe posts, however, the evaluation determined that the sign capacity of a post is determined by the breakaway assembly. The 2 ½ in. and 3 in. pipe posts used the same breakaway design and therefore the 3 in. pipe posts did not have any additional capacity over the 2 ½ in. post. As a result, the 3 in. post is redundant and was discontinued. This decision allows for a simplified inventory and eliminates confusion on pipe size. Maintenance can continue to utilize 3 in. pipe posts until the inventory is depleted but shall not order new 3 in. pipe posts. All existing 3 in. pipe posts shall be treated as 2 ½ in. posts for purposes of choosing posts using the post selection tables. 2 ½ in. pipe posts can be installed on existing 3 in. stubs.

Support. MoDOT utilizes two sizes of pipe post, 2 ½ in. and 4 in. An important fact to understand is pipe post sizes are based on the inside diameter (I.D.) of the pipe post and not the outside diameter, this is the industry standard for pipe measurement. This is critical in selecting the correct pipe from inventory as well as charging out the correct post to keep your inventory levels correct.

Pipe posts have a similar sign capacity as PSST, even though they would appear to be able to carry a larger sign load due to size and thickness of the steel pipe. While the post themselves are far stronger than PSST, it is the breakaway of the pipe post which controls the sign load capacity of the post. The heavy-duty construction of a pipe post is not specifically related to sign load capacity but is more directly related to the durability of the post. Unlike PSST, which must be replaced after each vehicular impact, pipe posts are constructed with much thicker steel so the signpost can be impacted by a vehicle without being damaged and reinstalled for continued use. There are many pipe posts on our right of way that have been there for two or three generations of signs and are still functional so while they are heavier and more expensive, they are a long term investment and are far more durable.

Pipe posts are used for single and double signpost assemblies to support signs up to 58.5 sq.ft. These posts are typically used on freeways and expressways where signs are larger, wind speeds can be higher due to more open right of way and the sign may see larger snow load impact from plows pushing more snow from across multiple lanes to the right side of the roadway.

Pipe posts are also the preferred post to support large route assemblies, especially on freeways and expressways. In the past, Wide Flange posts were once used to support these assemblies (and many remain in place) as the design of the post was well suited to attaching a series of backing bars needed to support the assemblies. However, the multi-direction breakaway and high resistance to torsional or twisting forces makes pipe posts the preferred post over the Wide Flange design.

Pipe posts are designed and fabricated with the breakaway device as part of the post / stub combination; as long as the post and stub breakaway is assembled correctly the post is capable of being impacted from any direction. Details for the assembly of this post system are found in Standard Plans 903, special attention must be paid to the placement of three breakaway bolts, the required and proper placement of all washers within the breakaway and most critically to the proper tightening and torque of the breakaway bolts.

Standard. If Pipe posts are used, they shall be either 2 ½ in. or 4 in. in size. The size and number of posts shall be determined using the post selection tools. Pipe posts shall be installed in accordance with Standard Plans 903.

903.3.4.5 Wide Flange (I-Beam) Posts

Support. MoDOT uses 6 sizes of Wide Flange posts, commonly referred to as Design #1, #2, #3, #4, #5 and #6, increasing in size and capacity respectively. Wide Flange posts are typically used to support signs 30 ft2 and larger and are MoDOT’s highest capacity ground-mount sign support. As with Pipe Posts, Wide Flange post are designed to be a more durable post intended to last multiple generations of signs and designed to be able to be impacted by vehicle and then reassembled and reused.

Wide Flange post are designed and used to support large structural signs, signs made using extruded aluminum panels instead of flat sheet aluminum. The cross section of a wide flange post being that of an I-beam permits structure signs to be easily attached to the post using post clips or “dog clamps” instead of using traditional sign bolts. These posts are traditionally used on freeways and expressways only; however, there may be special applications where they may be used on two lane roadways if the size of the sign is too large for other post options.

Wide Flange posts were once the standard to support large route assemblies on freeways and expressways, however, over time two weaknesses were identified that changed this direction, making Pipe posts the better option. The two weaknesses of Wide Flange posts used to support route assemblies are:

  • Safety - Route assemblies many times are installed in and around intersections and in these locations it is theoretically possible some assemblies could be impacted from any direction of travel. Single Wide Flange posts are only breakaway in two directions and are not designed to be breakaway if impacted on either side, just the front and back of the sign. Pipe posts are designed as a multi-breakaway post and can be impacted from any direction making them the better option for these installations.
  • Torsional / Twisting Force Resistance – Although Wide Flange posts are very strong, they do have a limited resistance to twisting moments when installed as a single post installation. In wind prone locations, sign assemblies on a single Wide Flange post can begin to twist in the wind, and if this continues long enough, it can cause the post to fatigue and break off at the base. Pipe posts have an extreme resistance to twisting and can resist much larger torsional forces compared to wide flange posts.

As with Pipe Posts, Wide Flange posts are fabricated with the breakaway system as part of the post / stub assembly. While Wide Flange posts have a breakaway assembly at ground level like Pipe posts, they also require a hinge system located directly below the sign. The hinge system permits the wide flange post (the portion from the ground to the bottom of the sign) to swing up out of the way of a vehicle when impacted without the upper portion of the post and the sign needing to move. This reduces the mass that a vehicle must move when it impacts the post and in return reduces the impact energy to the car.

Unlike all other MoDOT posts, there are minimum post spacing which must be taken into consideration when selecting the correct number and size of post. Wide Flange Posts are much heavier than any other MoDOT post and hitting two of these posts at the same time in most cases would impart too much energy to the vehicle and would not meet minimum breakaway standards. These special considerations are included in Standard Plans 903 which contains all of the fabrication and installation details for Wide Flange Posts, however, due to their critical nature they are also listed here:

  • Wide Flange Post Designs #1 and #2 have no minimum post spacing requirements.
  • Wide Flange Post Designs #1 or #2 shall not be installed in three post configurations supporting signs less than 11 feet width.
  • Wide Flange Post Designs #3, #4, #5 and #6 shall be spaced at least 7 ft. apart.

The post selection tool is designed to utilize two post installations over three post installations to help address minimum post spacing; it also reduces the number of footings which need to be constructed. However, there are some general rules based on sign size used to judge the number post for different size ranges of signs:

  • Signs between 6 ft. and 17 ft. wide will typically be supported on two posts
  • Signs wider than 17 ft. will typically be supported by three posts
  • Signs of any size are not recommended to be installed on one Wide Flange post

Standard. If Wide Flange posts are used, they shall be either a structural #1, #2, #3, #4, #5 or #6 in design. The size and number of posts shall be determined using the post selection tools. Wide Flange posts shall be installed in accordance with Standard Plans 903.

903.3.5 Secondary Sign Supports – Post Extensions

Support. These supports are 3 in. aluminum I-Beam used to attach exit number panels to the top of, or to hang a secondary sign below, structural signs on new installations. Details of these posts are shown in the Standard Plans 903.

Option. There are occasions where modifications and/or additions must be made to existing sign installations where the existing posts are not long enough to support the new sign assembly. In these cases, it is permissible to utilize secondary sign supports to effectively extend the primary signposts to support signs a maximum of 3 feet taller than the existing primary signposts.

Secondary sign supports may only be used to allow taller signs to be installed on existing signposts if the signposts have the capacity to carry the larger sign based on signpost selection tools.

If a new sign assembly is more than 3 ft taller than the existing primary signposts, new signposts shall be installed.

903.3.6 Backing Bars

Support. Backing bars are typically used to support and stiffen wide flat sheet signs mounted on single signpost or to help support the individual signs which make up sign assemblies to form one unified sign assembly. Details for backing bars can be found in Standard Plans 903.

903.3.7 Breakaway Assemblies

Standard. All signposts installed on right of way shall meet federal breakaway standards and MoDOT standards. Signposts not meeting current standards, but met the standards at the time of their installation, may remain in place until the end of their service life.

Sign trusses and other large sign support structures that are not breakaway shall be protected by acceptable shielding, such as guard rail or barrier wall.

Support. 4 in. x 4 in. wood posts do not need any modification to be breakaway, however 4 in. x 6 in. and 6 in. x 6 in. wood posts will need to be cross drilled to meet breakaway standards. U-Channel posts do not require breakaway modifications if they are direct driven into the ground, however, if the ground stub and slice installation method is used the installation will need to be installed according to the Standard Plans 903 to meet breakaway requirements. PSST will require breakaway devices added in certain applications based on sign and number of posts used for an installation. The signpost selection tools will indicate when a breakaway is required for PSST posts. Pipe and Wide Flange posts have the breakaway devices integrated into the post design.

903.3.8 Sign Orientation (MUTCD Section 2A.20)

Support. The orientation of the face of a sign in relation to the driver and roadway is critical to visibility and legibility, especially at night. The effectiveness of the retroreflective sheeting on a sign can be negatively impacted if the orientation of the sign face is not correct, due to incorrect installation and/or a signpost being damaged and knocked out of alignment.

The orientation of a sign can also help reduce unwanted reflection or glare off of the sign face. The skew angle, shown in Standard Plans 903, is designed to help address this glare issue for tangent sections.

Guidance. Unless otherwise provided in the EPG, signs should be vertically mounted at approximately right angles to the direction of, and facing, the traffic that they are intended to serve, with an approximate 3 degree skew angle away from traffic.

Signs that are placed 30 ft. or more from the pavement edge should have a skew angle that is turned toward the road to improve the effectiveness of the retroreflective sheeting.

Option. While the standard skew angle is 93 degrees, the skew angle may be adjusted to maintain brightness and avoid glare for signs on curved sections of road. On roadways with significant grades, sign faces may be tilted forward or back from vertical position to improve the viewing angle.

903.3.9 Sign Mountings (MUTCD Section 2A.21)

Support. Attaching a sign properly to a sign support is critical in order to properly orient the sign in relation to the driver as well as provide a durable, long life installation.

Standard. Plastic/nylon washers shall be used between the heads of all twist fasteners (such as screws, bolts or nuts) and the sign face to protect the sheeting from the twisting action of the fasteners.

Signs shall be attached to each type of sign support in accordance with Standard Plans 903.

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