903.3 Ground-Mounted Sign Supports - Revision history

TaracksA at 14:20, 11 November 2025

2025-11-11T14:20:02Z

← Older revision		Revision as of 09:20, 11 November 2025
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	[[Category:~~903 Highway Signing~~\|903.03]]		[[Category:Backup Removed Pages\|903.03]]

TaracksA: /* 903.3.4 Ground-Mounted Sign Support Selection */

2025-10-20T17:11:10Z

903.3.4 Ground-Mounted Sign Support Selection

← Older revision		Revision as of 12:11, 20 October 2025
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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.		:* 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==		=={{SpanID\|903.3.4}}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.		'''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.

Hoskir: /* 903.3.3.1 Mounting Height – U-Channel, Wood, Perforated Square Steel Tube (PSST) and Pipe Posts (MUTCD Section 2A.18) */ updated per email from Tom H.

2024-03-28T18:32:32Z

903.3.3.1 Mounting Height – U-Channel, Wood, Perforated Square Steel Tube (PSST) and Pipe Posts (MUTCD Section 2A.18): updated per email from Tom H.

← Older revision		Revision as of 13:32, 28 March 2024
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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		:* 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) and ~~Pipe~~ Posts (MUTCD Section 2A.18)===		===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 and ~~pipe~~ 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.		'''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.		The 7-foot mounting height also applies to all freeway and expressway applications to enhance long distance visibility.

Hoskir: updated per RR3683

2023-05-01T16:00:39Z

updated per RR3683

← Older revision		Revision as of 11:00, 1 May 2023
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	\|'''Forms'''		\|'''Forms'''
	\|-		\|-
	\|[[Media:903.2a_Signpost_Selection_Guide_2022.xls\|Signpost Selection Guide]]		\|[[Media:903.2a_Signpost_Selection_Guide_2022-5-23.xls\|Signpost Selection Guide]]
	\|-		\|-
	\|[[Media:903.2aPrintableSignpostSelectionGuide_2022.xls\|Printable Signpost Selection Guide for use in the field]]		\|[[Media:903.2aPrintableSignpostSelectionGuide_2022.xls\|Printable Signpost Selection Guide for use in the field]]

Hoskir: /* 903.3.4.3 Perforated Square Steel Tube Posts (PSST) */ Updated per RR 3613 - added table

2023-01-12T15:12:43Z

903.3.4.3 Perforated Square Steel Tube Posts (PSST): Updated per RR 3613 - added table

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

Kleins1: /* 903.3.4.3 Perforated Square Steel Tube Posts (PSST) */

2022-11-28T21:34:10Z

903.3.4.3 Perforated Square Steel Tube Posts (PSST)

← Older revision		Revision as of 16:34, 28 November 2022
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	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.		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.'''		'''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.''' 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.		'''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.

Kleins1: /* 903.3.4.3 Perforated Square Steel Tube Posts (PSST) */

2022-11-28T18:08:34Z

903.3.4.3 Perforated Square Steel Tube Posts (PSST)

← Older revision		Revision as of 13:08, 28 November 2022
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	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.		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 ~~interstates~~, ~~freeways~~ and ~~expressways~~ shall be installed using concrete footings.		'''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.		'''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.

Hoskir: updated 2 forms - Signpost Selection Guide

2022-10-24T17:21:24Z

updated 2 forms - Signpost Selection Guide

← Older revision		Revision as of 12:21, 24 October 2022
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	\|'''Forms'''		\|'''Forms'''
	\|-		\|-
	\|[[Media:903.~~2a Signpost Selection Guide 2021~~.xls\|Signpost Selection Guide]]		\|[[Media:903.2a_Signpost_Selection_Guide_2022.xls\|Signpost Selection Guide]]
	\|-		\|-
	\|[~~https~~:~~//epg.modot.org/documents/~~903.~~2aPrintableSignpostSelectionGuide~~.xls Printable Signpost Selection Guide for use in the field]		\|[[Media:903.2aPrintableSignpostSelectionGuide_2022.xls\|Printable Signpost Selection Guide for use in the field]]
	\|}		\|}
	'''Guidance.''' Signs should be ground-mounted whenever possible unless mounting overhead is justified or required.		'''Guidance.''' Signs should be ground-mounted whenever possible unless mounting overhead is justified or required.

Hoskir: /* 903.3.4.4 Pipe Posts */

2022-10-24T16:51:06Z

903.3.4.4 Pipe Posts

← Older revision		Revision as of 11:51, 24 October 2022
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	'''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.		'''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 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 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 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.		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.

Hoskir: /* 903.3.4.4 Pipe Posts */

2022-10-24T15:44:21Z

903.3.4.4 Pipe Posts

← Older revision		Revision as of 10:44, 24 October 2022
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	===903.3.4.4 Pipe Posts===		===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.		'''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.		'''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 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.
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	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 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.		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.		'''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.