Work Zone - 6.01 Temporary Traffic Control
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6.01 Temporary Traffic Control
Temporary traffic control devices used in work zones are required by FHWA to meet the requirements of Part 6 of the MMUTCD.
Federal regulations also require all roadside devices, such as portable sign stands, barricades, barrier terminals, crash cushions and other work zone hardware to be compliant with NCHRP 350 and / or MASH crash test requirements.
Devices used on MDOT facilities must also follow the requirements detailed in MDOT’s Standard Specifications for Construction, and other policy related documents.
Sometimes it is necessary to decrease spacing in between channelizing devices to keep vehicular traffic out of the work zone. It is not acceptable to use caution tape to tie channelizing devices together in the roadway.
6.01.01 Cones
Cones used on freeways and other high-speed highways must be a minimum of 28 inches tall. The exception to this rule allows 18-inch cones to be permitted for the protection of uncured pavement markings where no static lane closures are used.
Cones smaller than 42 inches in height are prohibited for use at night on all MDOT roadways.
6.01.02 Plastic Drums
Drums must be provided as detailed in WZD-125 and meet the requirements detailed in section 812 and 922 of the MDOT Standard Specifications for Construction. The spacing between plastic drums on roadways must follow the guidelines outlined below in Table 6-1 Channelizing Device Maximum Spacing.
Exhibit 6-1: Fluorescent Drum
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Table 6-1: Channelizing Device Maximum Spacing
| Work Zone Speed Limit | Taper | Tangent |
|---|---|---|
| < 45 mph | S | 2 X S |
| ≥ 45 mph | 50 feet | 100 feet |
6.01.03 42-Inch Channelizing Devices
42-inch channelizing devices (grabber cones) are recommended when a plastic drum restricts the proposed lane widths to less than 11 feet, including shy distance.
Exhibit 6-2: 42-Inch Channelizing Device
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Grabber cones are recommended for Capital Preventive Maintenance (CPM) projects such as
chip seal, micro-surface, concrete repairs, and crack seal applications, or any daytime closure
lasting less than 12 hours.
They are also recommended for use when lane closures are required to install pavement markings on freeways.
If cones are specified in the contract, use of 42-inch channelizing devices may be permitted at the expense of the contractor. Lights on 42-inch channelizing devices are not allowed.
When 42-inch channelizing devices are used during nighttime work the devices spacing is a maximum distance of 50 feet apart in tangent sections, and a maximum of 25 feet apart in tapers. These spacing requirements apply for all speed limits.
Grabber cones weigh less than plastic drums and require ballast for different conditions. 30 lb. ballasts are recommended for freeways and 15 lb. ballasts are recommended for non-freeways.
6.01.04 Tubular Markers
(Updated 1/20/2020)
Use of tubular markers should only be considered after other channelizing devices have been ruled out. Tubular markers are not a recommended channelizing device unless used to separate traffic or work operations. They may be used in work zones where more permanent delineation (attached to the pavement) may be required during winter shutdown.
Exhibit 6-3: Tubular Markers
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Tubular markers are required to be a minimum of 28 inches in height. Markers less than 42 inches should have two three inch white reflectorized bands placed at the top, and markers 42 inches or greater should have four 4- to 6- inch wide alternating orange and white stripes with the top stipe being orange.
6.01.05 Delineators
Delineator panels are not allowed for channelizing but may be used for roadside safety delineation based on engineering judgment.
Flexible delineators, delineator panels, and flexible guardrail delineators are used along narrow shoulders, next to an open ditch section on 3R and 4R freeway projects as described in WZD126-A. Flexible delineators and delineator panels should be located one foot off the edge of the paved shoulder and spaced at a maximum distance of 200 feet, unless otherwise directed by the Engineer.
Other types of delineation devices include; concrete barrier reflectors, guardrail reflectors, and lateral clearance markers and must be included in the TTCP.
Exhibit 6-4: Flexible Delineator
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Exhibit 6-5: Delineator Panel
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Exhibit 6-6: Flexible Guardrail Delineators
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6.01.06 Barricades
(Updated 5/28/2021)
Barricades are used to control traffic by closing, restricting or delineating all or a portion of a roadway.
Exhibit 6-7: Type III Barricade
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Only Type III barricades are allowed for use with motorized traffic on MDOT projects.
Barricades are equipped with reflective sheeting that is intended to be a directional indicator. Stripes angled down to the right indicate passing on the right, whereas angled down to the left indicates passing on the left. Stripes angled down to the middle of the barricade indicate a closure. Stripes angled upward to the center of the barricade indicate passing on both sides.
Type III barricades are required to have two working type C lights or two working type D attached, as detailed in WZD-125 and MDOT’s Standard Specification for Construction.
6.01.07 Temporary Barriers
(Updated 1/20/2020)
Barriers are devices designed to prevent or reduce work zone penetration by vehicles while minimizing injuries to vehicle occupants. They are designed to provide positive separation of motorists from workers, bicyclists, and pedestrians. Types of barrier protection include concrete barriers, movable barriers, prefabricated steel barriers, and water filled barrier walls.
A temporary barrier wall should be installed on a compacted aggregate or paved surface. This surface must be flush with the surface adjacent to the barrier. If a limited deflection barrier is used it must be on a surface as detailed in Standard Plan R-53.
Barriers are required to meet quality standards contained in the current edition of the American Traffic Safety Services Association (ATSSA) Quality Guidelines for Temporary Traffic Control. Temporary traffic barriers are required to meet NCHRP 350 and / or MASH crash testing criteria, meeting a minimum of Test Level 3.
Barrier endings must be located outside of the clear zone or fitted with an impact attenuator, as detailed in Standard Plan R126. Additional information on temporary barriers is available in Section 7.01.67 and 7.01.68 of the Roadway Design Manual. See table 6-8 Edge Drop-off Treatments for detailed barrier wall use information.
Consideration should be given to extend the barrier wall past the work area, both upstream and/or downstream to encompassed materials, equipment and work operations. Worker access to the job site should also be protected when practical. The length of need should be shown or detailed in the internal traffic control plan. Each location should be evaluated to determine the length of need, as a best practice a range of 100 to 300 feet is recommended. The following tables include elements to consider when deciding on the use of barriers and examples of typical barrier applications.
Table 6-2: Barrier Use Considerations
| Drop offs greater than or equal to 12 inches, that
will not be backfilled overnight |
| Unprotected features (walls, piers, sign
structures, foundations, etc.) |
| Interim unprotected items (i.e. non-standard
slopes, stockpiles, ditches within the roadway clear zone, etc.) |
| Proximity to and severity of hazards |
| Duration of exposure |
| Size of work area available |
| Traffic exposure to opposing traffic |
| Contractor mobility and ingress / egress |
| Volume of traffic |
| Work zone speed |
| Barrier deflection distance |
| Vertical / horizontal roadway alignment |
| Hazard presented by barrier itself once it is in
place |
| Hazard presented to pedestrians and traffic
during barrier placement |
Table 6-3 Barrier Use Typical Applications
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The following alternatives to using temporary barriers should be considered due to risks to drivers and workers during placement and removal of the devices:
- Buffer lane closures
- Nightly backfill of excavations
- Tapers
- Temporary detours or crossovers
- Additional or closer spacing of channelizing devices and extra warning signs
Barriers must be used on freeway projects where opposing traffic lanes are shifted and are adjacent to each other.
A. Movable Barriers
Movable barrier walls are designed to move laterally as a unit to close or open a traffic lane. Adequate storage sites at both ends of the barrier are required for the barrier transfer machine. Movable barrier walls meet NCHRP 350 and MASH Test Level 3.
Exhibit 6-8: Movable Barrier Operation
INSERT PICTUREB. Mobile Barrier Walls
(Added 12/3/2020)
Mobile barrier walls are devices that function similar to the traditional temporary barrier wall. Mobile barrier walls provide for positive protection of workers during mobile and short term work when temporary barrier is not practical and are transported and operated via a single semi-truck. Mobile barrier walls are required to meet NCHRP 350 or MASH Test Level 3. Check with the WZDE for any questions on using mobile barrier walls on projects.
Exhibit 6-9: Mobile Barrier Wall Devices
INSERT PICTUREC. Water Filled Barrier
Consideration for using this barrier should be limited to low speed, low volume roadways where an improvement over the use of traffic cones or drums is needed. Water filled barrier walls should not be used as a replacement for concrete barrier walls due to their large deflection.
D. Barrier Endings (attenuation)
Within the clear zone, the approach ends of temporary barriers, are fitted with impact attenuators to reduce the potential for occupant injury during a vehicle collision with the barrier. Details for placement of impact attenuators on approach ends of the barriers may be found in the Standard Plan R-126. WZD-175 covers one layout of sand module impact attenuators.
If work extends into a time frame in which the weather could drop below freezing, the manufacturer’s recommendation for anti-freeze treatments must be followed when using a water filled attenuator system.
E. Mobile Attenuators
(Updated 5/28/2021)
Truck mounted attenuators (TMA) and trailer mounted attenuators are referred to as mobile attenuation as described in the Frequently Used Special Provision 20SP812(A). Mobile attenuators are recommended to protect personnel or equipment in certain cases. For more detailed information and guidelines on the placement of mobile attenuators, reference Chapter 8 Maintenance and Surveying Operations.
6.01.08 Temporary Signs
(Updated 12/3/2020)
Work Zone signing can range from ground driven wood supports to portable temporary roll-up signs. The size of the sign and the duration and location of the work will determine which type of sign should be used. All temporary signs must be crash tested to meet the requirements of National Cooperative Highway Research Program Report 350 (NCHRP 350) or Manual for Assessing Safety Hardware (MASH). The size of sizes must follow table 6F-1 Temporary Traffic Control Zone Sign and Plaque Size of the MMUTCD.
While it is not required for all projects, it is recommended to show the specific temporary sign locations on the plans or location detailed in the special provision for maintaining traffic. This effort during design will assist in providing more accuracy in the field to ensure proper placement and reduce the number of obstructions and conflicts.
A supplemental plaque is recommended when signs are located on a side street leading into where the work is taking place. A route marker or the road name should be used and can be spelled out if space allows as shown in Exhibit 6-10.
Sign design for projects can be very elaborate with specific guidance found in Section 6.01.11.
Exhibit 6-10: Road Name Plaque
INSERT PICTUREA. Ground-Driven Temporary Signing
Ground-driven temporary signing mounted on conventional driven sign supports should be used for projects that last more than fourteen days. Portable sign supports should be used when it is not possible to use ground-driven sign supports.
Cover or remove existing signs that can be misinterpreted or that may not apply during construction. Signing must be reviewed throughout the life of the project to ensure messages are current and meet the needs of the motorist.
B. Portable Temporary Signing
Portable temporary signing is generally used in short term and mobile work zone operations where frequent repositioning of the signing is necessary to keep pace with the work along the roadway. Portable temporary signs must be mounted on crashworthy sign supports at a 5 foot bottom height, including signs located in the closed section of a walkway. If erecting signs behind a curb, or within 6 feet of a pedestrian walkway, mount signs at a bottom height of at least 7 feet above ground.
Portable sign systems should not be left up unless active work is taking place. When signs are removed they must be stored in accordance with the section titled “Temporary Signs” in 812 of the Standard Specifications for Construction.
Portable sign supports should only be used with the recommended ballast for wind conditions approved by the manufacturer. If signs cannot withstand wind conditions in the field, they should be ground-driven or work postponed until conditions allow work to take place safely.
When a Leap Frog traffic control method is used, it requires additional sets of signs to increase productivity and mobility, project offices should pay for two additional sets of temporary signing. The operation places signs in the correct location and has them stored on the ground and then stands the signs up in the new location and lays the signs down as the operation progresses down the road. The additional sets of signing will keep the operation moving, thus lessening the number of days needed to complete the work.
C. Portable Temporary Signing – Roll-up
Signs made of roll up material must not be used at night or during hours of darkness. This includes early mornings before the sun rises.
D. Innovative Temporary Signing
(Added 1/20/2020)
In areas with limited space or specific geometric features traditional temporary sign may not function ideally so the use of innovative signs should be evaluated.
1. Concrete Barrier-Mounted Temporary Sign System
In locations with concrete barrier wall and limited space the Barrier mounted sign should be considered. The condition of the existing barrier wall should be evaluated during the design phase to verify the condition. In areas with limited shoulder width the size of the sings can be reduced as detailed in table 6F-1 Temporary Traffic Control Zone Sign and Plaque Size of the MMUTCD. For more details on this device see the section titled “Concrete Barrier-Mounted Sign System” in the MDOT Standard Specifications for Construction.
2. Temporary Water Filled Base Sign System
In locations that don’t allow for temporary signs to be post driven an alternative to consider is a water filled base sign system. This sign system provides a sturdy base without the need to drive into the ground. Ideal locations are bridge decks or paved shoulders.
This sign system can also be utilized in lieu of type III barricades in locations where there is a high potential for devices to be moved by the motoring public. The next weight of the system is above 400 lbs when filled with water. For more detailed information see the recommended special provision Temporary Water Filled Base Sign System-12RC812-A445
6.01.09 Sign Covers
(Updated 12/3/2020)
Temporary sign covers must cover the entire legend or symbol when the sign is less than 60 square feet. The material used needs to be opaque during all light and weather conditions. Lifting devices cannot remain attached to the sign covers. When sign covers are removed, they must be laid flat on the ground. See “Sign Covers” in Division 8 of the Standard Specifications for Construction for additional details.
When covering overhead signs or signs larger than 60 square feet, the contractor is not required to cover the entire sign but must ensure conflicting information is covered, using a Type 1 sign cover. Placing a closed sign across an exit sign as shown in exhibit 6-10 provides the motorist with the best information and allows them to understand which exit is closed.
Exhibit 6-11: Sign Covers
INSERT PICTUREFor additional information See “Sign Covers” in Division 8 and 9 of the Standard Specifications for Construction.
Existing signs must be covered or removed and replaced with the appropriate temporary regulatory signing. Sign covers not in use must be stored in accordance with 6.01.10. Additional information is provided in the MMUTCD Part 6 (Section 6F.07).
A. Directional Guide Signs
< 24 hours
When a detour is to be placed for 24 hours or less, all existing conflicting permanent signs should be covered as determined by the Engineer.
> 24 hours
When a detour is to be placed for more than one day, all existing conflicting permanent signs must be covered.
B. Overhead Signs
The covering of overhead signs is always recommended but may not always be practical. For this reason, the requirements will be determined at the project level and detailed in the plans. The message and length of the project should be used when determining what signs will be covered or modified. Projects lasting longer than 14 days should have overhead signs covered. Also see page 812 of the Construction Manual for in depth guidance on overhead sign covers.
C. Regulatory Signs
Regulatory signs, such as speed limits, with contradictory information must be covered.
6.01.10 Signing Coordination
When projects have traffic control that overlaps with another project, a coordination clause should be developed for all projects that are affected. If multiple projects are going to be in the same location, a removable marking or tag may be considered for tracking and payment purposes. Requiring project numbers or permanent identifiers must not be used.
6.01.11 Project Specific Signing
(Updated 12/3/2020)
Unique and special temporary signs must be detailed (i.e. SignCAD) and included in the contract documents. Special temporary sign locations should be specified in the TTCP and the special provision for maintaining traffic.
When designing project specific signing, motorist comprehension of the sign and the meaning needs to be considered. If the information on the sign cannot be quickly processed by a passing motorist who is not familiar with the area, multiple signs may need to be utilized. It is recommended to have a person not familiar with the project review the design to determine if the sign is easily understood. Follow the Temporary Sign Design Guidelines in Appendix K.
6.01.12 Temporary Pavement Markings
Temporary pavement markings are installed in work zones to provide road users with a clearly defined path for travel through the work zone.
The two types of temporary pavement markings designated in the pay items, include Removable “Type R" and Non-Removable “Type NR".
Temporary wet reflective pavement markings increase guidance through the work zone during dry and wet conditions. Temporary wet reflective pavement markings may be paint or preformed tape and must be selected based on the pavement surface and time of year they are placed. Temporary Type R Tape and Type NR Paint pavement markings must be wet retroreflective.
For additional details please see the section titled “Temporary Pavement Markings” in section 812 of the Standard Specifications for Construction and PAVE 904-A Temporary Longitudinal Line Types & Placement.
Temporary markings must be removable if applied to the pavement surface course, unless lines are painted in the final configuration and the final marking is not a durable marking. Type R tape should not be used on courses other than the surface course unless the marking is removed prior to paving.
Type NR Tape pavement markings may be used to mark the base and leveling courses of asphalt and need not be removed. Type NR Tape is not to be used on any final surface course.
Payment for removing pavement markings, when necessary, will only be made for Type NR markings.
Temporary pavement marking products approved for use are listed on MDOT’s Qualified Product List.
A. Pavement Marking Removal
Non-applicable or inappropriate permanent pavement markings must be removed before making any changes in the traffic pattern that will last longer than three days. This may be done using grinding, air, or water blasting. Painting over existing markings is not allowed per section 812.03.F of the Standard Specifications for Construction.
Scarring caused by the removal of temporary markings can result in a permanent shadow of a line that may be followed by a motorist. Temporary markings must be designed and placed such that abrasive removal techniques that result in the scarring are not used. To prevent scarring that could confuse a road user out of their lane, temporary wet reflective removable tape should be used in shift / taper sections.
B. Shift Markings
(Updated 12/3/2020)
All temporary traffic shifts (except merging tapers) on freeways should be striped with 6inch solid Wet Reflective Type R, Tape. 6inch solid edge and lane lines must be placed 300 feet prior to the traffic shift, through the shift, and 300 feet after the traffic shift. This is required for both entry and exit shifts.
To provide contrast on concrete surfaces, a 4-inch white line may be used next to a 4inch black contrast line. A field review should be conducted prior to choosing this method to ensure the black contrast tape does not conflict with existing crack seal.
Non-freeway shifts (except merging tapers), must be striped with 4-inch solid Wet Reflective Type R, Tape edge lines and lane lines must be placed 150 feet prior to the traffic shift, through the shift, and 150 feet after the traffic shift. This is required for both entry and exit shifts.
The leading and trailing markings described above are used to provide motorists with additional guidance and reassure the driver they are in the correct location, as the lane lines will have just been modified.
C. Temporary Raised Pavement Marks (TRPM), Type 3
TRPM, Type 3, may also be used to supplement edge line markings in temporary crossovers and traffic shifts. Spacing of devices should be at a minimum of 25-foot intervals beginning 250 feet in advance of the cross over shift and ending 250 feet beyond the crossover point on the tangent section.
D. Pavement Marking Cover
Covering existing markings with black Type R tape is allowed when specified in contract documents or as directed by the Engineer. Covering existing markings is typically done on short term tapers or in areas with frequent lane closure changes and must be done with black tape.
E. Curing Compound Removal
On newly paved concrete surfaces, the cuing compound should be removed prior to placing temporary markings. Removal of curing compound prior to placing temporary markings on new concrete must be done by water blasting. This will minimize the scarring of the surface. If the final markings are going to be placed in the same location, water blasting is not required.
F. Edge Line Markings
Temporary edge lines should be placed on new pavements in place for longer than three days or drums placed at 200 foot spacing or 42-inch channelizing devices placed at 100 foot spacing may be used to delineate the shoulder. Edge line markings are recommended for placement after 14 days. If temporary edge line markings are not placed after 14 days, the reasons should be documented.
Broken line applications of temporary paint or tape are not acceptable for edge line delineation. If the project requires striping in stages, it should be striped with temporary wet reflective markings until landscaping is complete, excluding water and cultivating.
G. Capital Preventative Maintenance (CPM) Projects
For CPM Micro-Surfacing projects, temporary pavement markings application and guidelines should be as described in Frequently Used Special Provision 12SP-811(E)-03, located on the frequently used special provision page.
For cold mill one course HMA overlay and one course HMA overlay projects, the previously special provision, 12RC811-A475.pdf, can be used, which specifies that pavement markings should be placed at the end of the work day:.
For chip seal, micro surface, and crush and shape projects, place Temporary Raised Pavement Markers (TRPM) – Type 1, in accordance with the manufacturer’s specifications to mark the centerline of the roadway. TRPM’s should be removed prior to placing permanent markings. Space TRPMs at 25 feet (6F.79 of the MMUTCD).
6.01.13 Lighting
(Updated 1/20/2020)
6.01.14 Arrow Boards
(Added 12/3/2020)
6.01.15 Portable Changeable Message Sign (PCMS)
6.01.16 Temporary Traffic Signals
6.01.17 Automated Flagger Assistance Device (AFAD)
(Updated 12/3/2020)
6.01.18 Glare Screening
(Updated 1/20/2020)
6.01.19 Transverse Temporary Rumble Strips
(Updated 12/3/2020)
6.01.20 Existing Longitudinal Rumble Strips
6.01.21 Pilot Vehicles
6.01.22 Innovative Traffic Control Devices
6.01.23 Rolling Roadblocks
(Added 1/20/2020)
