616.13 Other TTC Zone Design Features and Safety Devices (MUTCD Chapter 6M)
616.13.1 General (MUTCD Section 6M.01)
Support. Although certain devices and design features, such as lighting, barriers, dividers, crash cushions, and screens, are sometimes used in TTC zones to supplement traffic control devices or enhance traffic operations or safety for road users, they are not considered to be traffic control devices. The following Sections describe the most commonly used devices and design features. EPG 911 (MUTCD Section 1D.04) contains additional information about these devices and design features.
616.13.2 Positive Protection and Temporary Traffic Barriers (MUTCD Section 6M.02)
Support. Temporary traffic barriers, including portable or movable barriers, are devices designed to help prevent penetration by vehicles while minimizing injuries to vehicle occupants, and to protect workers, bicyclists, and pedestrians.
Positive protection devices means devices that contain or redirect vehicles and meet applicable industry crashworthiness evaluation criteria.
Additional information for temporary traffic barriers is located in EPG 617, Specifications Section 617, Standard Plan 617.20, and Standard Plan 619.10.
Standard. At a minimum, agencies shall use positive protection devices in work zones with high anticipated operating speeds that provide workers no means of escape from motorized traffic intruding into the workspace unless an engineering study determines otherwise. An engineering study shall include at a minimum the information as approved by the Highway Safety and Traffic Division.
Positive protection devices shall be considered in other situations that place workers at increased risk from motorized traffic, and where positive protection devices offer the highest potential for increased safety for workers and road users.
Considerations for positive protection shall include, but are not limited to, the following circumstances:
- A. Work zones on roadways that provide workers no means of escape from motorized traffic such as tunnels or bridges;
- B. Long-term stationary work zones of two weeks or more resulting in substantial worker exposure to motorized traffic;
- C. Projects with work zone operating speed limits of 45 mph or greater, especially when combined with high traffic volumes;
- D. Work operations that place workers, pedestrians, or bicyclists close to travel lanes open to traffic; and
- E. Roadside hazards, such as drop-offs or unfinished bridge decks, that will remain in place overnight or longer.
Temporary traffic barrier shall be required on the following:
- A. Roadway excavation edge drop-offs (refer to Standard Plan 619.10), and
- B. Bridge rehabilitation jobs with bridge rail replacement and/or full depth repair.
Guidance. Temporary traffic barrier should be considered for long-term bridge repair work.
Support. When specified, quantities are calculated and shown on the plans. Delineators for temporary concrete traffic barriers are provided at no direct pay as shown on Standard Plan 617.20 and stated in Specifications Section 617. Delineators pay items are used only to retrofit existing permanent concrete traffic barrier.
Work zone setups vary depending on the nature of the positive protection used.
23 CFR Part 630.1108(a) contains additional requirements for certain projects.
Option. Temporary traffic barriers may be used to separate two-way vehicular traffic.
Standard. Temporary traffic barriers shall be supplemented with standard delineation, pavement markings, or channelizing devices for improved daytime and nighttime visibility if they are used to channelize vehicular traffic. The delineation color shall match the applicable pavement marking color.
Temporary traffic barriers, including their end treatments, shall be crashworthy (see definition in EPG 911 (MUTCD Section 1C.02)).
Short intermittent segments of temporary traffic barrier shall not be used because they nullify the containment and redirective capabilities of the temporary traffic barrier, increase the potential for serious injury both to vehicle occupants and pedestrians, and encourage the presence of blunt leading ends. Adjacent temporary traffic barrier segments shall be properly connected in order to provide the overall strength required for the temporary traffic barrier to perform properly.
Guidance. Appropriate channelizing devices and pavement marking should always be used in front of barrier tapers for lane closures, shoulder closures or transition areas for temporary bypasses or connections. Wherever practical, a lateral shy distance should be provided between the edge of the driving lane and the barrier. A longitudinal buffer area should be provided between the channelizer taper and the barrier taper.
Support. Temporary traffic barrier includes portable concrete, portable steel, or movable barrier which can all be moved laterally and/or longitudinally when needed and/or from site to site. More specific information on the use of temporary traffic barriers is contained in Chapters 8 and 9 of “Roadside Design Guide,” 4th Edition, 2011, AASHTO and EPG 617.1.
616.13.3 Temporary Raised Islands (MUTCD Section 6M.03)
Standard. Temporary raised islands shall be used only in combination with pavement striping and other suitable channelizing devices.
Option. A temporary raised island may be used to separate vehicular traffic flows in two-lane, two-way operations on roadways having a vehicular traffic volume range of 4,000 to 15,000 average daily traffic (ADT) and on freeways having a vehicular traffic volume range of 22,000 ADT to 60,000 ADT.
Temporary raised islands also may be used in other than two-lane, two-way operations where physical separation of vehicular traffic from the TTC zone is not required.
Guidance. Temporary raised islands should have the basic dimensions of 4 inches high by at least 12 inches wide and have rounded or chamfered corners.
The temporary raised islands should not be designed in such a manner that they would cause a motorist to lose control of the vehicle if the vehicle inadvertently strikes the temporary raised island. If struck, pieces of the island should not be dislodged to the extent that they could penetrate the occupant compartment or involve other vehicles.
Standard. At pedestrian crossing locations, temporary raised islands shall have an opening or be shortened to provide at least a 60-inch wide passageway for the crossing pedestrian.
616.13.4 Detectable Edging for Pedestrians (MUTCD Section 6M.04)
Support. Individual channelizing devices, tape or rope used to connect individual devices, other discontinuous barriers and devices, and pavement markings are not detectable by persons with vision disabilities and are incapable of providing detectable path guidance on temporary or realigned sidewalks or other pedestrian facilities.
Guidance. A continuously-detectable edging should be provided throughout the length of a temporary pedestrian facility such that it can be followed by pedestrians using long canes for guidance. This edging should extend at least 8 inches above the surface of the sidewalk or pathway, with the bottom of the edging a maximum of 2 inches above the surface. This edging should be continuous throughout the length of the facility except for gaps at locations where pedestrians or vehicles will be turning or crossing. This edging should consist of a prefabricated or formed-in-place curbing or other continuous device that is placed along the edge of the sidewalk or walkway. This edging should be firmly attached to the ground or to other devices. Adjacent sections of this edging should be interconnected such that the edging is not displaced by pedestrian or vehicular traffic or work operations, and such that it does not constitute a hazard to pedestrians, workers, or other road users.
Support. Examples of detectable edging for pedestrians include:
- A. Prefabricated lightweight sections of plastic, metal, or other suitable materials that are interconnected and fixed in place to form a continuous edge.
- B. Prefabricated lightweight sections of plastic, metal, or other suitable materials that are interconnected, fixed in place, and placed at ground level to provide a continuous connection between channelizing devices located at intervals along the edge of the sidewalk or walkway.
- C. Sections of lumber interconnected and fixed in place to form a continuous edge.
- D. Formed-in-place asphalt or concrete curb.
- E. Prefabricated concrete curb sections that are interconnected and fixed in place to form a continuous edge.
- F. Continuous temporary traffic barrier or longitudinal channelizing barricades placed along the edge of the sidewalk or walkway that provides a pedestrian edging at ground level.
- G. Chain link or other fencing equipped with a continuous bottom rail.
Guidance. Detectable pedestrian edging should be orange, white, or yellow and should match the color of the adjacent channelizing devices or traffic control devices, if any are present.
616.13.5 Crash Cushions (MUTCD Section 6M.05)
Support. Crash cushions are systems that mitigate the effects of errant vehicles that strike obstacles, either by smoothly decelerating the vehicle to a stop when hit head-on, or by redirecting the errant vehicle. The two types of crash cushions that are used in TTC zones are stationary crash cushions and truck-mounted attenuators. Crash cushions in TTC zones help protect the drivers from the exposed ends of barriers, fixed objects, shadow vehicles, and other obstacles. Specific information on the use of crash cushions can be found in “Roadside Design Guide,” 4th Edition, 2011, AASHTO.
Standard. Crash cushions shall be crashworthy (see definition in EPG 911 (MUTCD Section 1C.02)). They shall also be designed for each application to stop or redirect errant vehicles under prescribed conditions. Crash cushions shall be periodically inspected to verify that they have not been hit or damaged. Damaged crash cushions shall be promptly repaired or replaced to maintain their crashworthiness.
Support. Stationary crash cushions are used in the same manner as permanent highway installations to protect drivers from the exposed ends of barriers, fixed objects, and other obstacles.
Standard. Stationary crash cushions shall be designed for the specific application intended.
An approved crash cushion shall be installed on the exposed end of the barrier where the posted speed prior to construction on an existing facility or the anticipated posted speed of a temporary facility is greater than 35 mph. A crash cushion shall be installed on the upstream end for divided facilities, and on both ends for all two-way facilities.
Truck- or trailer-mounted attenuators shall be energy-absorbing devices attached to the rear of shadow trucks and shall be used in accordance with the manufacturer’s specifications. If used, the shadow vehicle with the attenuator shall be located in advance of the work area, workers, or equipment to reduce the severity of rear-end crashes from errant vehicles.
Support. See EPG 612 for the use of protective vehicle and truck/trailer-mounted attenuators.
Trucks or trailers are often used as shadow vehicles to protect workers or work equipment from errant vehicles. These shadow vehicles are normally equipped with flashing arrows, changeable message signs, and/or high-intensity rotating, flashing, oscillating, or strobe lights and are located properly in advance of the workers and/or equipment that they are protecting. However, these shadow vehicles might themselves cause injuries to occupants of the errant vehicles if they are not equipped with truck-mounted attenuators.
Guidance. The shadow truck should be positioned a sufficient distance in advance of the workers or equipment being protected so that there will be sufficient distance, but not so much so that errant vehicles will travel around the shadow truck and strike the protected workers and/or equipment.
Support. Chapter 9 of “Roadside Design Guide,” 4th Edition, 2011, AASHTO contains additional information regarding the use of shadow vehicles.
616.13.6 Temporary Transverse Rumble Strips (MUTCD Section 6M.06)
Support. Temporary rumble strips are a strategy for reducing distracted driving and achieving MoDOT’s work zone safety goals. Temporary rumble strips are used in construction or maintenance work zones (planned and unplanned) and consist of temporary long-term rumble strips.
Temporary rumble strips (see JSP-13-04C) are comprised of a series of elongated strips installed laterally within the travel lane of the roadway to provide an audible and vibratory alert to drivers of the upcoming work zone.
Temporary long-term rumble strips are installed using adhesive backing on each strip to prevent movement of the strips in the travel lane.
Standard. If the color of a transverse rumble strip used within a travel lane is not the color of the pavement, the color of the rumble strip shall be orange.
When temporary long-term rumble strips are used, installation shall consist of a minimum of 1 set (5 strips per set) per open lane, spaced in accordance with Figure 616.13.6.1 on center with the RUMBLE STRIPS AHEAD sign.
If temporary rumble strips are used in work zones, any damage done to pavement shall be restored to the existing condition.
616.13.6.1 Temporary Rumble Strips for Work Zones
Standard. Temporary long-term rumble strips shall be used in long-term stationary daytime or night-time work zones with a duration of 3 days or more when a lane(s) is impacted.
Guidance. If the project is a long-term stationary project with intermediate construction activities impacting traffic, such as lane restrictions, additional temporary rumble strips should be evaluated for use.
Support. When temporary long-term rumble strips are included in projects performed by contractors, Job Special Provisions (JSPs) for temporary rumble strip used is required. Additional information, including maintenance, repair, and monitoring of temporary rumble strips, can be found in JSP-13-04C.
616.13.6.2 Placement of Temporary Rumble Strips for Work Zones
Support. Generally, temporary rumble strips are placed before the feature requiring attention (e.g., merge, lane shift, reduced speed) giving the motorist enough time to act safely. The recommended distance before the feature should be referenced or shown on the plans or figures. The location should be adjusted when needed to comply with the guidance below or based on performance observations.
Standard. Temporary rumble strips shall be placed perpendicular to traffic.
Guidance. The following information is applicable to temporary long-term rumble strips, except where noted.
- A. Temporary rumble strip placement should be reviewed, and consideration given to geometric conditions prior to placement.
- B. Temporary rumble strips should be place on tangent roadway segments. Placement at or just beyond a vertical curve crest should be avoided.
- C. Temporary rumble strips work best when in complete contact with the roadway surface and therefore should not be used on heavily rutted roadways or on roadways with loose material.
- D. Temporary rumble strips should not be placed through marked pedestrian crossings, marked pedestrian paths, or on marked bicycle routes. Engineering judgment should be used to avoid placement in these areas.
- E. Temporary rumble strips should not be placed where routine braking is expected on the rumble strip. Routine braking on the strips may cause the strips to come loose and require additional maintenance than otherwise would be needed to keep them in place. Relocating the rumble strips should be considered if constant maintenance is required.
- F. Additional sets of temporary long-term rumble strips should be used to get the attention of drivers.
Standard. Temporary rumble strips shall be checked, as necessary, for proper adhesion and corrected when needed. If temporary rumble strips are omitted as directed by this standard or field conditions, the decision with explanation of why, shall be documented accordingly.
616.13.7 Screens (MUTCD Section 6M.07)
Support. Screens are used to block the road users’ view of activities that can be distracting. Screens might improve safety and motor vehicle traffic flow where volumes approach the roadway capacity because they discourage gawking and reduce headlight glare from oncoming motor vehicle traffic.
See EPG 617.1 for additional information.
Guidance. Screens should not be mounted where they could adversely restrict road user visibility and sight distance and adversely affect the operation of vehicles.
Option. Screens may be mounted on the top of temporary traffic barriers that separate two-way motor vehicle traffic.
Guidance. Design of screens should be in accordance with Chapter 9 of “Roadside Design Guide,” 4th Edition, 2011, AASHTO.
616.13.8 Lighting for Night Work (MUTCD Section 6M.08)
Support. Utility, maintenance, or construction activities on highways are frequently conducted during nighttime periods when vehicular traffic volumes are lower. Large construction projects are sometimes operated on a double-shift basis requiring night work (see EPG 616.14.18).
Guidance. When nighttime work is being performed, floodlights should be used to illuminate the work area, equipment crossings, and other areas.
When used, floodlighting should be installed in a manner that minimizes glare to approaching road users, flaggers, or workers.
The adequacy of the floodlight placement and elimination of potential glare should be determined by driving through and observing the floodlighted area from each direction on all approaching roadways after the initial floodlight setup, at night, and periodically. Lighting should be sufficient so as to give road users the capability to identify a worker as a person. Care should be taken to minimize the potential for shadows to conceal workers within the work area.
Support. Desired work area illumination levels vary depending upon the nature of the task involved. An average horizontal luminance of 5 foot candles can be adequate for general activities. Tasks requiring high levels of precision and extreme care can require an average horizontal luminance of 20 foot candles.
Option. Typical work area lighting installations may include dirigible lighting, portable light towers, balloon lighting, lights attached to equipment or post-mounted lights. In some cases, existing lighting or ambient lighting may meet lighting level requirements and negate the need for including work zone lighting.
Support. Temporary fixed lighting illuminates specific areas of significance to guide road users within the TTC zone during nighttime hours.
Option. Temporary fixed lighting may be considered at gore areas, transitions, ingress and egress areas, equipment crossings, intersections, temporary signals, islands temporary bypasses, and crossovers. Temporary fixed lighting may also be considered for areas of potential conflict, such as temporary ramps, intersections, and one-lane, two-way traffic operations that are in place for more than 15 consecutive days. These conditions may require lighting even though the work may not be conducted at night. This type of lighting, while more difficult to design and install, provides more uniform light distribution thereby enabling the motorist to better navigate the work zone at night.
Guidance. When stationary operations exceed 15 consecutive days, such as a bridge replacement, interchange or intersection work that occurs at night, temporary fixed lighting should be considered in lieu of work zone lighting.
Standard. If temporary fixed lighting is used, it shall be designed and shown in the plans.
Support. Refer to Specifications Section 901 for roadway lighting requirements and EPG 901 for lighting design.
Standard. Except in emergency situations, flagger stations shall be illuminated at night.
616.13.8.1 Fleet Lighting
Support. Fleet lighting increases the visibility of work or incident response vehicles and equipment while in the temporary traffic control zone.
Standard. Except as provided in the following paragraph, all work vehicles and equipment shall be equipped with an acceptable warning light system, per example USDOT-approved warning lights. These lights shall be activated whenever a vehicle or piece of equipment is engaged in a work zone or incident response operation within the temporary traffic control zone.
Option. Vehicles and pieces of equipment may operate without warning lights activated if the vehicles and equipment are located within a workspace delineated by channelizers or protected by a temporary traffic barrier. For this situation, activation of the lights is not required.
Support. For Maintenance lighting requirements, see EPG 616.31. For construction projects see EPG 616.23.