Work Zone - 4.03 Work Zone Considerations
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4.03 Work Zone Considerations
Work zones should be planned and designed to consider work operations and address safety impacts for workers, traffic regulators, motorists, and nonmotorized users.
4.03.01 Work Zone Hazards
Each work zone should be assessed for hazards. The following provides a list of example conflicts for drivers, workers, and traffic regulators that designers should consider when developing the TTCP:
- Congestion related crashes
- Work zone crashes & crash patterns
- Roadway configuration, merging tapers and lane drops
- Unexpected queues
- Unstable traffic flow
- Lane widths
- Pavement markings
- Clear zone safety issues
- Drainage
- Lane departures
- Barrier wall and attenuation
- Roadway geometrics
- Vertical hazards, drop offs
- Emergency vehicle access
- Disabled vehicle refuges
- Night work visibility
- Confusing or conflicting signs, markings and features
Designers should also consider the following conditions for workers and traffic regulators when developing a work zone TTCP:
- Work zone protection
- Impaired or distracted drivers
- Errant vehicles
- Narrow work zones
- Equipment and materials storage
- Escape routes for workers
- Exposure to moving equipment
- Aggressive drivers
- Speeding drivers
- Vehicle crashes and crash patterns
- Work zone access (ingress / egress)
- Pedestrians/Non-motorized Traffic
- Shared use trails and paths
4.03.02 Workers
(Updated 12/3/2020)
Drivers experiencing long delays become impatient and can act unpredictably increasing worker exposure. Other driver conditions to consider include:
- Impaired drivers
- Drowsy drivers
- Distracted drivers
- Aggressive drivers
Designers should also take into account the position of the workers behind barrier walls. Unless the wall is secured to the pavement or has limited deflection, consideration should be given to improving or creating a lateral buffer space.
Barrier protected work zones should be considered on a project-by-project basis and not just for long term stationary projects.
In addition to the location of the workers and their proximity to traffic, the type of work taking place should be factored into the design of the TTCP.
Active work should not take place with traffic on both sides of the workers, on the same roadbed, unless there is positive protection. Traffic can be on both sides of a lane closure for concrete curing when no workers are present.
A. Traffic Regulators and Spotters
Traffic regulators are typically used to stop and direct traffic for work activities such as:
- One lane alternating traffic control
- Intersection control
- Road closures (Parades, Special Events, etc.)
- Short durations
- Spot locations
- Ingress and egress Locations
A spotter may be used to watch traffic and alert workers of an approaching errant vehicle.
The following are some TTCP considerations:
- Evaluate the necessity of using traffic regulators at night. If determined that traffic regulating is the most effective option for the TTCP, the engineer should review and approve the lighting plan and layout prior to the start of construction. Balloon Lighting is required for traffic regulator stations.
- Traffic regulators must not be utilized on freeways at any time. Haul road crossing may require a traffic regulator and should be reviewed and approved by the project office.
- The traffic regulator’s location, escape route, protection and other safety related issues should be incorporated into the traffic regulator station.
- Law enforcement may be used for some traffic regulator operations. See Section 4.05 Work Zone Law Enforcement, for information on how to include enforcement in projects.
- Spotters may be used to decrease worker exposure when applicable. Intended spotter locations should be shown on the TTCP.
Detailed information on traffic regulator procedures and conduct is available through the resources included in Appendix G (Resources).
4.03.03 Road Users
(Updated 12/3/2020)
The message conveyed to the user through signing, pavement markings, and devices must be concise and consistent.
A. Drivers
Drivers and their passengers account for a large portion of work zone fatalities. It is important to provide a TTCP that effectively guides and protects drivers while traveling through the work zone. Effective planning and design of work zones should be considered from the driver’s perspective.
To provide adequate time to react and make rational decisions to navigate safely, the work zone impact mitigation strategies should be easily understood by motorists.
Temporary channelization and alignment should be modified to the work zone conditions. MDOT work zone guidelines and typicals should be followed; however modifications that improve the safety and operations of the work zone should be made according to field conditions. Changes should be documented in the Inspector’s Daily Report (IDR).
The riding surface is important for the safety of motorcycle riders. Whenever possible, construction operations should be avoided that place motorcycles on grooved pavement, pavement lane edge drops from milled surfaces, rumble strips and unpaved surfaces. If these conditions cannot be avoided, the TTCP should include adequate warning signs for these conditions to alert the motorcycle riders. Consideration should also be made for ingress/egress points, where designs should include the capability of a motorcyclist accessing the roadway perpendicular to differentials in pavement elevations.
B. Non-Motorized Users
Adequate facilities should be provided to allow non-motorized users to travel through or around the work zone. Requirements and guidance on maintaining non-motorized user traffic in work zones are found in Chapter 5: Non-Motorized Work Zone Safety and Mobility.
C. Oversized Vehicles
If the TTCP for the proposed work zone does not allow vehicles that exceed the legal width, height or weight limits, notify the region/TSC transport permit agent. Warning signs notifying vehicles of the restriction must be provided. On some projects, it may be necessary to designate a detour route for oversized vehicles.
4.03.04 Work Zone Crash Reduction Strategies and Mitigations
(Updated 1/20/2020)
According to the MDOT Trunkline Crashes in Work Zones Report (2012), the five primary crash types in work zones are:
- Rear-end straight (RE-ST)
- Sideswipe-same direction (SS-SM)
- Fixed object (FXOBJ)
- Other object (O-OBJ)
- Angle-straight (AN-ST)
The five primary crash types have accounted for approximately 80% of trunkline work zone crashes from 2002 to 2014. Each type may be related to several work zone factors. Potential crash reduction strategies for the TTCP design and during construction are shown in the tables below. Please contact the WZDE for additional methods or option details.
Table 4-1: Work Zone Crash Reduction Strategies and Tools: Rear End Crashes
| Work Zone Crash Factors | Crash Reduction Strategy | Crash Reduction Tools |
|---|---|---|
| Speed | Review Work Zone Speeds |
|
| Additional devices |
| |
| Uniformed Law Enforcement Presence |
| |
| Geometry | Review Work Zone Lane Closure / Shift Tapers |
|
| Review sight distance and operation at intersections and driveways within the work zone |
| |
| Access | Review ingress and egress of work zone vehicles |
|
| Signing for work zone ingress and egress locations |
| |
| Capacity / Congestion | Additional warning for motorists |
|
| Accelerated construction techniques: working / lane closure time restrictions |
| |
| Minimized number of stops / delay improvement |
| |
| Alternate Route |
| |
| Review MOT staging, look at ways to add lanes (capacity) |
| |
| Delineation and Signs | Additional warning signs for approaches and high traffic volume driveways |
|
| Review work zone devices at intersections and driveways within the work zone |
|
Table 4-2: Work Zone Crash Reduction Strategies and Tools: Sideswipe-Same Direction Crashes
| Work Zone Crash Factors | Crash Reduction Strategy | Crash Reduction Tools |
|---|---|---|
| Speed | Review work zone speeds |
|
| Intelligent Transportation System (ITS) speed warning signs |
| |
| Geometry | Increase lanes and/or shoulders widths, where possible |
|
| Review Traffic Shift and Lane Closure Taper Lengths |
| |
| Delineation and Signs | Review configurations for Yield, Merge, or Acceleration Lanes |
|
| Review travel path delineations |
| |
| Additional signs for traffic merge / shift locations |
| |
| Add delineations |
| |
| Pavement markings |
|
Table 4-3: Work Zone Crash Reduction Strategies and Tools: Fixed-Object Crashes
| Work Zone Crash Factors | Crash Reduction Strategy | Crash Reduction Tools |
|---|---|---|
| Work Zone Speed | Review work zone speeds |
|
| ITS speed warning signs |
| |
| Delineation and Signs | Place object markers at fixed object locations near travel path |
|
| Add delineation |
| |
| Fixed Object Location | Remove, relocate, or protect fixed object |
|
Table 4-4: Work Zone Crash Reduction Strategies and Tools: Other Object
| Work Zone Crash Factors | Crash Reduction Strategy | Crash Reduction Tools |
|---|---|---|
| Delineation and Signs | Frequent inspection and review location and placement of temporary devices (signs, drums, barricades, channelizing devices, etc.) | |
| Delineate travel path from objects and devices |
| |
| Speed | ITS speed warning signs |
|
| Review work zone speeds |
|
Table 4-5: Work Zone Crash Reduction Strategies and Tools: Angle Crashes
(Added 1/20/2020)
| Work Zone Crash Factors | Crash Reduction Strategy | Crash Reduction Tools |
|---|---|---|
| Signal and ITS | Advance warning flashers |
|
| Review signal head placement and timing |
| |
| Geometry | Review turning movements |
|
| Review intersection and stopping sight distance |
| |
| Delineation and Signs | Additional advance intersection signing |
|
| Review travel path |
| |
| Pavement markings & advance warning |
|
4.03.05 Accommodations Table
(Added 5/28/2021)
Table 4-6 has been developed to provide guidance and information to the design and development of the work zone and traffic restrictions for projects and is focused on specific operations, not the overall MOT. The overall project MOT plan should be determined using the MOT Decision Tree which is detailed in section 1.02.08. This table is designed to be used as a tool to assist not only design staff in the development of a project but also as a starting point for construction staff to utilize with contractors to verify that certain work types and their considerations are evaluated.
In situations where a work activity is listed in Table 4-6 and does not have the recommended traffic restrictions in place for that specific operation, this table is a starting point for discussions. Documentation for modifying restrictions that have been placed on the project, should reference this table when appropriate. Due to the nature of work zones and different factors to consider, each location, operation, and project as detailed in the rest of this chapter should be considered when evaluating, discussing and considering a traffic restriction modification. This table allows a platform for the contractor to start a discussion on operations that may have been overlooked during the design process. If an operation is listed in the table and is defined or restricted, or an operation is not covered within the project documents but is listed in the table, correspondence to discuss this should take place with the contractor. If required, an onsite meeting should take place. During this correspondence, the project engineer and the contractor should work toward a mutually agreed-upon solution otherwise the contractor should be provided with the justification and reasoning behind why this traffic restriction is in place. This correspondence in no way guarantees a modification to the traffic restrictions but will serve as support and validation for the final decision. Deviations will be granted on a case-by-case basis, and only for the specific operation in question.
Table 4-6: Accommodations for Specific Work Activities
| Activity | Maintaining Traffic Considerations |
|---|---|
| Survey of Existing/Field Measurements; Restoration & Clearing, Mowing; Delivery of Materials | These activities have minimal impact to traffic and may include stationary shoulder closures. If shoulders are not available, consider how contractor equipment and materials will safely be delivered to the work site. If minimal impact work is expected to be completed at night because of closure restrictions, include specifying night work for these activities. Avoid wording in contract language indicating that "all work shall be performed at night…”. |
| Shoulder Corrugations, aggregate shoulders | Production rates for this work is approximately 1 mile per hour. To minimize worker exposure of multiple closure setups, extended lane closure lengths should be considered during design for this operation and included in the contract language. For non-freeway work, “leap-frog” operations should be considered as a best practice. Extended closure lengths for this work will not be a determination of project significance regarding a TMP. |
| Workers in an open trench | Trench work should be planned for daytime operations. In the event of required night work, a lighting plan must be approved per the contract documents, and the duration and occurrence of the work operation should be minimized. |
| Concrete pavement repairs | Patches should be marked utilizing stationary lane closures with mobile attenuators; layout at night is not recommended. Utilize a mobile attenuator for saw-cutting operations. Shift traffic away from patches when feasible. Shoulder improvements including widening may be necessary to accommodate shifted traffic. If widening is not feasible, then daytime closure or a full closure should be utilized. For roadways with 3 or more lanes, adjacent lanes should be closed for active work and reopened for curing. Patches in the vicinity of an entrance ramp may require a full ramp closure or other restrictions on the ramp; traffic shifts into a ramp merge area require either a ramp closure or yield/stop conditions for the ramp. |
| Structures: Bridge painting, bridge deck work | For work on scaffolding or lifts and/or work with no means of escape, utilize positive protection such as mobile attenuators, mobile barrier wall, or concrete barrier. |
| Setup, drop off, removal of temporary traffic control | These activities are permitted to be completed with a mobile shoulder operation and should avoid peak times for a particular roadway. Narrow work areas less than ten feet should utilize a moving closure with attenuator/work convoy using the appropriate typical. |
| Temporary Rumble Strips (Orange) in Advance of a Work Zone | Include off peak stationary lane closure and/or mobile lane closure times in the maintaining traffic special provision. Mobile attenuators should be included for this work. |
| Work Convoys, Pothole patching, guardrail, and attenuator maintenance | Repairs and maintenance within a lane of traffic on freeways that require immediate attention must utilize mobile operations with mobile attenuators unless a stationary closure can be set up. Law enforcement assistance should be considered. Preventative repairs should utilize off-peak moving closure depending on work type. |
| Traffic switches/shifts | Freeway traffic switches may require closing of additional lanes and ramps, these time frames should be detailed in the maintenance of traffic special provision. Consideration should be given to allow extended ramp closure for the traffic switch operations without a detour plan depending on ramp volumes. Projects with temporary markings require detailed staging plans. If a traffic switch is planned at night, MDOT should coordinate law enforcement presence into the contract. See section 6.05.11 and 6.05.12 for more detailed information. |
| Covering signs | Consider how signs will be covered when not within planned lane closure limits. |
| Signal work | Avoid wording in contract indicating that “…work is only allowed between 9am – 3pm”. Less impactful closures (e.g. closing turn lanes, sidewalk work) should be considered prior to 9am and after 3pm |
