Work Zone - 6.01 Temporary Traffic Control

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

S = Work Zone Speed Limit (mph)

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

To keep vehicular traffic from entering work areas, such as excavations or material storage sites.

To separate workers, bicyclists, and pedestrians from motor vehicle traffic. See Chapter 5 for more information.

To separate opposing directions of freeway traffic.

Where drums or cones do not provide adequate guidance for the motorist or for the protection of the worker.

Where workers are exposed to unusually hazardous traffic conditions.

Where existing traffic barriers and bridge railings are removed during a construction stage.

On all bridge work where a precipitous drop-off is within 4 feet of the toe of the barrier closest to the active traffic lane. Examples of precipitous drop-offs include but are not limited to: Bridge deck work with open holes in the deck. Bridge railing removed

On projects where scaffolding or other structures or equipment with workers overhead are in place for three days or more.

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: MOVEABLE BARRIER OPERATION INSERT PICTURE

B. 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 PICTURE

C. 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)

6.01.09 Sign Covers

(Updated 12/3/2020)

6.01.11 Project Specific Signing

(Updated 12/3/2020)

6.01.13 Lighting

(Updated 1/20/2020)

6.01.14 Arrow Boards

(Added 12/3/2020)

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)

6.01.23 Rolling Roadblocks

(Added 1/20/2020)

Categories

• Work Zone Safety and Mobility Manual Index
• Chapter 6: Traffic Control Devices and Implementation