Work Zone - 8.06 General Traffic Control Guidelines
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8.06 General Traffic Control Guidelines
Temporary Traffic Control (TTC) is a very important part of any maintenance or surveying operation. The purpose of this section is to provide guidance on the placement of TTC devices in maintenance and surveying work zones.
All traffic control devices used on projects must be crashworthy and meet MDOT requirements. See the Materials Quality Assurance Procedures Manual for the current crashworthiness requirements and standards for Work Zone Devices.
It is required that the MMUTCD, Part 6 be followed at a minimum to ensure that all traffic control devices used in work zones meet current standards.
Care must be taken to ensure that traffic control devices do not obstruct or intrude on the usable width of sidewalks, temporary paths, or other pedestrian facilities. For more information on how to facilitate pedestrian facilities see Chapter 5.
For more detailed information on traffic control devices see Chapter 6.
8.06.01 Regular Work Zone Inspections
The work zone should be driven on a regular basis to ensure the adequacy and condition of all traffic control devices on the project. During work zone inspections, traffic control should be compared to the applicable maintaining traffic typical(s) for the project.
During poor weather conditions such as rain or high winds, the frequency of inspection should be increased to make sure all devices are performing properly. If TTCD start to fail due to weather conditions crews should pick-up and postpone work.
8.06.02 Partial Lane Closures
Partial lane closures should be avoided where traffic is not being shifted. If any part of a lane is to be occupied, the entire lane must be closed to traffic. Shifting a lane is permitted as long as there is appropriate space for it.
8.06.03 Temporary Signs
Portable temporary signing is generally used for short term maintenance and mobile operations. Temporary warning signs are used to alert traffic of an upcoming maintenance or surveying operation. Diamond shaped orange warning signs should be 48" × 48" in size. Reflectorized signing is required.
For closures in non-pedestrian areas a five (5) foot minimum bottom height is required and driven posts are required for closures over 14 days. In pedestrian areas a seven (7) foot minimum bottom height is required.
For visibility, signs should be placed within six (6) to twelve (12) feet of the edge of the traveled lane or no closer than two (2) feet to the back of curb. Engineering judgement of lateral spacing should be applied in situations where the sidewalk butts up to the curb or there is no area for the sign between the curb and buildings in downtown areas.
If the work within stationary closure moves more than two (2) miles from the original signing sequence, a new signing sequence should be set-up and the original sequence removed.
Temporary signing must be covered, stored, or removed when work ceases in accordance with the section titled “Temporary Signs” in Section 812 of the Standard Specifications for Construction. If roll-up signs are used they must be completely folded up and stored properly, or removed from the shoulder.
If it is determined that a lower speed limit must remain in place to maintain work zone safety/integrity, reduced speed signs may remain posted.
See Chapter 6 for more information about warning signs. See the MDOT Traffic and Safety Typicals for sign spacing requirements.
8.06.04 Existing Permanent Signs
Existing permanent signing in the work zone which conflicts with temporary signs must be covered in accordance with the section titled “Sign Covers” in Section 812 of the Michigan Department of Transportation’s Standard Specifications for Construction. Sign Covers should be removed when work ceases. Signs must be covered so that the reflective material is not damaged by scratching or crushing cells or by moisture.
Additional information on covering signs can be found in 6.01.9, Sign Covers
8.06.05 Channelizing Devices
Channelizing devices are used to warn road users of conditions created by work activities and to guide road users through the work zone. Channelizing devices include cones, grabber cones, plastic drums, and in some cases tubular markers where spacing is not adequate for other devices. Channelizing devices must be used to separate the work zone from traffic. More information about these devices, including the required spacing, can be found in Chapter 6 of this manual. Information about the taper and buffer lengths for channelizing devices can be found in the MDOT Traffic and Safety Typicals.
8.06.06 Traffic Regulators
Maintenance operations, particularly on two-lane, two-way roadways, often necessitate the use of Traffic Regulators. Prior to performing work, all Traffic Regulators must review the training requirements described in Section 1.05.03 Traffic Regulator Training.
Exhibit 8-1: Traffic Regulator
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8.06.07 Arrow Boards
Type A, B, and C arrow boards must have a solid rectangular appearance. A Type D arrow board must conform to the shape of the arrow. See figure 6F-6 in the MMUTCD for the requirements of each arrow board type.
- Type Aarrow displays are appropriate for use on low-speed urban streets.
- Type B are appropriate for intermediate-speed facilities and for maintenance or mobile operations on high-speed roadways.
- Type C arrow displays are intended to be used on high-speed, high-volume motor vehicle traffic control projects.
- Type D arrow panels are intended for use on authorized vehicles. Type D arrow panels may not be used without prior approval from the TSC traffic representative.
The minimum mounting height of an arrow panel should be 7 feet from the roadway to the bottom of the panel, except on vehicle-mounted panels, which should be as high as practical.
For Mobile operations where a lane is closed, the arrow board should be located to provide adequate separation form the work operation to allow appropriate reaction by approaching drivers.
A lighted arrow board is required on a TMA when the TMA is parked on the shoulder or within a lane. A lighted arrow board is not required on a TMA if it is located outside of the shoulder and is delineated by plastic drums.
All arrow boards shall be finished in non-reflective black. The arrow board shall be mounted on a vehicle, a trailer, or other suitable support. Arrow boards mounted on vehicles cannot be used for traffic regulating operations.
See 6.01.14 for more information about arrow boards.
Exhibit 8-2: Excerpt of Advance Warning Arrow Board Display Specification from Figure 6F-6 from the MMUTCD
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