Guidelines on Use of Exposure Control Measures
This document describes considerations and requirements of payment for temporary traffic control (TTC). The document offers several recommended methods and presents the advantages and disadvantages of each. Also addressed are techniques the agency and the contractor can use to monitor the effectiveness of selected methods.
This document is organized into the following sections:
- Examples of Exposure Control Measures
- Full Road Closures - Diversions
- Median Crossovers
- Ramp Closures
- Rolling Roadblocks
- Working During Nighttime Hours
- Accelerated Construction Techniques - Selecting and Implementing Exposure Control Measures
- Table of Benefits and Implementation Factors for Various Measures
- Examples: Minnesota, Oklahoma, Iowa, Florida, Washington
As defined in the federal regulation 23 CFR 630 Subpart K, exposure control
measures are traffic management strategies used to avoid work zone crashes
involving workers and motorized traffic by eliminating or reducing traffic through work zones. Exposure control can be achieved by diverting
traffic away from the work space, reducing the duration of work zones, and/or reducing the number of work zones
that motorists encounter.
Implementation of one or more exposure control measures in a work zone should be
considered where appropriate, but with adequate thought given to the
potential impacts of such measures on traveler mobility. Excessive delays or
queues created upstream or on other roadways due to the use of an exposure
control measure in a work zone can lead to rear-end and other types of traffic crashes that more
than offset the reduction in crashes in the work zone itself. Thus, the use of exposure control measures should be
considered in the context of the overall transportation management plan for a project.
There are three main approaches to reducing work zone exposure. The first
approach is to reduce the number of work zones by using longer lasting materials and performing quality work to
increase the period between when work is needed. The second approach is to reduce the duration that the work
zones are needed. The third
approach is to reduce or remove traffic from the work area.
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This guide focuses on the latter two approaches. Reducing the duration of work zones and the amount of interaction between workers and tariffic can be achieved through several strategies:
• full road closures;
• diversions;
• median crossovers;
• ramp closures;
• rolling roadblocks;
• working during nighttime hours; and
• accelerated construction techniques.
In addition to reducing work zone exposure, these strategies often make it
easier for work crews to complete tasks safely, which can result in improved productivity rates and higher
quality products.
Description
A full road closure is the removal or suspension of traffic operations either
directionality or bidirectionally from a segment of roadway for the purpose of reconstruction and/or maintenance
activities. During a full road closure, traffic is detoured usually for a predetermined amount of time,
allowing contractors full access to road- way facilities. All traffic normally using the facility must use alternative
routes or modes in the corridor. Full road closures can be implemented for a single night or weekend, for a few weeks
or can last a year or more.
Benefits
A full roadway closure allows the construction or maintenance crew to have access to the entire facility. As a result, conflicts (and ultimately, crashes) between work activities and traffic are eliminated. The strategy can also significantly reduce project completion time, and potentially improve work quality. The strategy creates the opportunity to complete multiple work tasks during a single closure.
Implementation Considerations
This strategy requires a significant amount of lead time to incorporate the necessary planning, out- reach, and other traffic management preparatory work required in the corridor before it is implemented. Because full road closures require the availability of adequate alternative routes and modes for motorists to use, the involvement of city and county agency personnel in the planning process is critical. To maintain credibility, it
is critical that the project meet the deadline established and publicized for reopening the road.
is critical that the project meet the deadline established and publicized for reopening the road.
Diversions
Description
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Benefits
One of the main advantages of using a diversion is that traffic flow is
maintained within the agency’s right-of-way, reducing the impacts to nearby alternative routes. As a result, the amount
of analysis of those routes and efforts to upgrade them to handle additional traffic is reduced.
Implementation Considerations
A diversion does require the construction of temporary pavement and possibly
channelization, lighting, and other devices, potentially increasing the time
and cost of the project. Consequently, the strategy is probably best suited to bridge projects or other work zones that are limited in both
length and duration.
Implementation Considerations
• high early-strength concrete;
Financial incentives can also be created for contractors to be innovative and aggressive when developing project schedules, or can be used as financial disincentive if a proposed completion schedule is not met. Each hour that a project is reduced in duration results in potential crash savings to motorists and workers.
Description
A median crossover is used to close entirely one side at a time of a divided
multi-lane highway, and move all traffic to the other side as a two-way operation (often with a median barrier
separating opposing traffic flows to prevent head-on collisions). This strategy allows work activities to occur on
the closed side, separated from traffic by a significant distance. In some instances, crossovers will need to
make full use of all existing pave- ment on the other side, including existing shoulders, in order to maximize
traffic capacity provided. (See the Typical Application 39 on page 5.)
Benefits
Similar to the diversion strategy, a median crossover maintains traffic flow
within the agency’s right-of-way,
reducing the impacts on nearby alternative routes.
reducing the impacts on nearby alternative routes.
Implementation Considerations
It is important to first verify that a median crossover strategy can provide
adequate traffic capacity. Temporary pavement must be constructed in the median of the roadway at both ends of the
project, adding to the overall cost of the project. Lengthy crossover sections can create challenges in
maintaining ramp access to cross streets. An appropriate design speed should be used for the temporary crossover. Care
must be taken to ensure that newly-created roadside hazards are adequately protected, and that the work area
access points near and in the
crossovers are adequately designed and delineated.
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Description
Another technique successfully used by some agencies to reduce vehicle exposure to work zones is to close temporarily the entrance and exit ramps upstream and within the limits of a work zone on an access-controlled facility. Ramp closures can be long-term over the duration of a project or project phase, or implemented during peak periods only on a daily basis.
Benefits
Ramp closures reduce exposure by causing drivers to seek out alternative routes. In addition, temporary ramp closures can also eliminate the need for complex traffic control to accommodate traffic entering and exiting the
facility. Furthermore, ramps can be restricted to high-occupancy vehicle (HOV)
use only, providing an incentive for carpooling/vanpooling and transit use
through the work zone.
Implementation Considerations
Ramp closures require consideration of the effects of detoured traffic on nearby local streets, emergency vehicle routes, and local businesses and residents. Adequate signing regarding alternate entrances and exits must also be provided. In some cases, trailblazing signs to the alternate ramps may be required. Failure to properly notify motorists of an exit ramp closure may actually increase work zone exposure by causing drivers who were planning to exit to instead travel through the work zone before exiting at the next downstream ramp.
Description
Many highway agencies and contractors use rolling roadblocks, also referred to
as traffic pacing. Typically, law enforcement vehicles with lights flashing enter the roadway upstream of the work
zone, and move at a fairly slow pace to create a blockage across all travel lanes. This creates a gap
between the law enforcement vehicles and the vehicles in front of the blockade. Rolling roadblocks are used when it
is important that no traffic be in the vicinity of a particular work activity for a short period of time (such as
during the lifting and placing of a bridge beam over an interstate).
Benefits
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This concept can also be applied during temporary traffic control set up and removal activities, allowing workers to finish the installation or removal process without having to interact with traffic constantly approaching and passing the temporary traffic control (TTC) crew. Given that TTC set up and removal activities tend to be overrepresented in work zone crash statistics, this technique can have substantial safety benefits for both workers and motorists.
Implementation Considerations
Rolling roadblocks require advance planning to determine the duration of gap
required and a high level of coordination and communication between law enforcement and the work crew to time
the work activity with the gap in traffic. Using signs to warn approaching traffic of the
slowdown is also important.
Description
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Another technique for reducing vehicular exposure to work zone
activities is to perform those activities at night (or on weekends) when traffic volumes are lower.
Benefits
Many agencies already limit temporary lane closures on high-volume roadways to nighttime hours in order to minimize the delays and queues that can develop during the day. Evidence suggests that this technique also has a significant safety benefit as well. As shown in the figure on the right, the dramatic reduction in traffic exposure at night results in lower crash costs per hour of work activity than working during
the day, and apparently more than offsets the perceived higher risks of impaired driving and reduced visibility
commonly associated with working at night.
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Not all work activities can be accomplished at night. In those cases, other strategies to reduce traffic volumes through work zones should be considered to reduce traffic volumes (e.g., public outreach campaigns, travel demand management techniques, etc.).
Working at night requires high-quality signing, advance notification to warn motorists, adequate lighting for workers, and measures to ensure safe traffic flows through the work zone. Agencies should pay special attention to avoid creating work zone lighting glare problems for approaching motorists.
In addition, working at night places increased stress on workers, supervisors, and inspectors. It is important
to encourage these individuals to take adequate rest breaks to ensure that they are fully alert (and remain so)
when at work.
Description
Techniques and strategies that encourage faster completion of construction and
maintenance efforts by the highway contractor can reduce motorist and worker exposure in work zones. A
number of techniques and technologies exist which can reduce the time it takes to rehabilitate or
reconstruct a roadway, or at least re- duce the amount of time that construction activities adversely impact travelers.
Some examples of such technologies include the use of:
• precast modular concrete road panels and bridge elements;
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• self-propelled modular transports (SPMTs) to move bridges fabricated completely off-site quickly into place on the roadway once the existing bridge is removed;
• full road closures to allow the contractor complete access to the entire roadway; and
• hot in-place asphalt recycling.
Financial incentives can also be created for contractors to be innovative and aggressive when developing project schedules, or can be used as financial disincentive if a proposed completion schedule is not met. Each hour that a project is reduced in duration results in potential crash savings to motorists and workers.
Common contract acceleration techniques include:
• design-build contracts;
• cost + time (A+B) bidding;
• incentive/disincentive clauses; and
• liquidated damages clauses.
When incentives are provided, contractors may be encouraged to utilize
accelerated construction techniques that are more costly.
Benefits
Accelerated construction can improve safety, work productivity, and work quality
while simultaneously minimizing the impacts of construction on traffic and the environment. Worker
and traveler safety are improved because the duration of the work (and thus traffic exposure) is reduced,
and because fewer iterations of temporary traffic control set up and removal
are needed (workers are often more vulnerable during these activities).
Experience suggests that construction acceleration techniques can often reduce
project durations by 10 percent or more.
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Implementation Considerations
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It is important that the values for incentives and for penalties established for the contract be properly balanced. Furthermore, it is important that agencies be able to accurately estimate reasonable completion dates and critical milestones for the project.
Finally, it is also important that the work be carefully planned, with appropriate safety precautions incorporated, to ensure production pressures do not lead to shortcuts that reduce safety or increase risk to workers.
Finally, it is also important that the work be carefully planned, with appropriate safety precautions incorporated, to ensure production pressures do not lead to shortcuts that reduce safety or increase risk to workers.
The table on page 9 provides some practical guidance on the implementation of
the various exposure control measures available. Determination of which measures or combinations of
measures is most appropriate for a given work zone must be made on a
project-by-project basis, considering construction phase sequencing, impact on overall project costs, effects on residents and businesses, and
other factors in addition to safety. Initial screening of possible approaches should occur during the
maintenance of traffic alternatives analysis. Those strategies that are not deemed feasible can be excluded. For
example, a lack of available nearby alternative routes may preclude the use of a full road closure strategy.
In all cases, judgment must
be applied to compare the project and societal costs of the strategies.
Benefits and Implementation Factors for Various Exposure Control Measures 
Full Road Closure, TH-36, St. Paul, Minnesota
The Minnesota Department of Transportation (DOT) implemented a full road closure
to rebuild a two-mile
section of trunk Highway 36, a primary commuter route in St. Paul. A number of innovative construction
techniques and traffic management strategies were employed, as well as contract incentives. The project was highly successful in many ways. Construction time was reduced from 19 months (for traditional construction methods) to only 6.5 months during the full road closure, which resulted in less traffic impact than would have otherwise occurred. No worker injuries or traffic incidents were reported during the project. A strong public
information campaign generated positive support for the strategy. A total of 90 percent of residents and com- muters gave the project positive ratings and 83 percent of the local businesses were pleased with the approach.
section of trunk Highway 36, a primary commuter route in St. Paul. A number of innovative construction
techniques and traffic management strategies were employed, as well as contract incentives. The project was highly successful in many ways. Construction time was reduced from 19 months (for traditional construction methods) to only 6.5 months during the full road closure, which resulted in less traffic impact than would have otherwise occurred. No worker injuries or traffic incidents were reported during the project. A strong public
information campaign generated positive support for the strategy. A total of 90 percent of residents and com- muters gave the project positive ratings and 83 percent of the local businesses were pleased with the approach.
Oklahoma DOT Ramp Closure Policy
The Oklahoma DOT instituted a formal policy that allows existing ramps to be
closed during rehabilitation
projects based on the potential for congestion or safety problems. To implement the policy, the DOT is required to conduct a public hearing for the surrounding neighborhoods to notify the public of the upcoming ramp
closure(s) and to address concerns expressed by the public. Initially, this hearing was conducted just prior to closing the ramp(s). However, the DOT is working to conduct hearings earlier in the planning and design phase to ensure that all local concerns are addressed and no economic hardship is created for the local economy by closing the ramp(s).
projects based on the potential for congestion or safety problems. To implement the policy, the DOT is required to conduct a public hearing for the surrounding neighborhoods to notify the public of the upcoming ramp
closure(s) and to address concerns expressed by the public. Initially, this hearing was conducted just prior to closing the ramp(s). However, the DOT is working to conduct hearings earlier in the planning and design phase to ensure that all local concerns are addressed and no economic hardship is created for the local economy by closing the ramp(s).
The Oklahoma DOT has indicated that the policy generally allows for construction
to be accelerated more than would be possible if the ramp(s) were left open. In
addition, the DOT believes that the public awareness of the project and of work
zones in general will increase due to the ramp closure(s) and has generated
useful suggestions on how to further reduce traffic impacts.
Median Crossover Design Guidance, Iowa DOT
The Iowa DOT established specific design and implementation guidance regarding
the use of median crossovers on four-lane divided highways. The guidance specifies that the crossover should
be designed for the posted speed of traffic prior to construction, but can be reduced by up to 10 miles
per hour if necessary. The crossovers are also to be located so as to minimize horizontal and vertical curvature sight
restrictions approaching the crossover. In addition, no access points are to exist in the crossover area so
that drivers can fully attend to negotiating the crossover without concern for entering or exiting traffic.
Florida DOT Traffic Pacing (Rolling Roadblock) Guide
The Florida DOT developed a design standard that specifically addresses the use
of traffic pacing (or rolling roadblock) operations. The standard includes the following sections:
• general notes;
• traffic control plans and technical specifications;
• main lane pacing details; and
• pacing operation design details.
The required project-specific traffic control plan, which should be developed
prior to initiating any traffic pacing operation, is outlined in the traffic control plan and technical
specifications sections. Establishing fail-safe “stop points” at exit ramps, in the event that a construction problem creates a condition
that can not be immediately cleared, and pacing operations to divert all traffic to the
exit ramp are required. The main lane pacing details a four-step process for getting traffic control
officers onto the travel lanes to initiate a traffic pacing operation and for getting them off of the roadway at
the conclusion of an operation. Finally, the pacing operation design details identify the calculations needed to
determine how long the pacing operation must be to allow the desired work activity to occur.
Washington DOT Use of SPMT
A full-depth, precast concrete deck replacement was completed in 2004 for Lewis
and Clark Bridge on SR 433 crossing the Columbia River between Oregon and Washington. SPMTs with a
specially designed lifting
and transporting frame were used to install 103 full-depth, full-width, prefabricated, precast, lightweight concrete deck panels
supported by longitudinal steel beams. One panel was replaced per night within a 6-hour period. Time constraints allowed full closures from 9:30 p.m. until 5:30 a.m.
Monday through Thursday. The deck replacement was completed in only 124 nights plus three weekend closures.
Conventional deck replacement would have required replacing the deck lane by lane over a 4-year period,
closure for several months, or closure every weekend for 6 months. Perhaps more importantly, the use of
SPMTs allowed the bridge to remain open for normal weekday operation.
How Can I Locate More Information Regarding This Topic?
Full Road Closure for Work Zone Operations: A Cross-Cutting Study. Report No.
FHWA-OP-04-009. FHWA, U.S. Department of Transportation, Washington, DC. August
2003. Available at http://ops.fhwa.dot.gov/wz/resources/publications/FullClosure/CrossCutting/its.htm
Flick, G., E.T. Cackler, S. Trost, and L. Vanzler. Time-Related Incentive and
Disincentive Provisions in Highway Construction Contracts. NCHRP Report No.
652. TRB, National Research Council, Washington, DC. 2010. Accessed at http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_652.pdf
Ullman, G.L., M.D. Finley, J.E. Bryden, R. Srinivasan, and F.M. Council. Traffic
Safety Evaluation of Nighttime and Daytime Work Zones. NCHRP Report No. 627.
TRB, National Research Council, Washington, DC. 2008. Accessed at http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_627.pdf
Use of Police Traffic Services in Work Zones. Maryland State Highway
Administration, Office of Traffic Safety. August 2005. http://www.marylandroads.com/OOTS/01Police.pdf
Barnard, R.K. A Mix of Innovations Succeeds in Minnesota. In Public Roads, Vol.
72, No. 6, May/June 2009. Accessible at http://www.fhwa.dot.gov/publications/publicroads/09june/02.cfm
Median Crossovers. Design Manual, Chapter 3, Cross-Section. Iowa Department of
Transportation, Iowa City, IA. Revised May 2007. Accessible at http://www.iowadot.gov/design/dmanual/03e-03.pdf
Traffic Pacing. Design Standard Index 655. Florida Department of Transportation,
Tallahassee, FL. July 2009. Accessible at http://www.dot.state.fl.us/rddesign/rd/rtds/10/655.pdf
Bryden, J.E., and D. Mace. Guidelines for Design and Operation of Nighttime
Traffic Control for Highway Maintenance and Construction. NCHRP Report No. 476.
TRB, National Research Council, Washington, DC. 2002.
Accelerated Construction. Office of Operations, FHWA, U.S. Department of
Transportation. Accessible at http://ops.fhwa.dot.gov/wz/construction/accelerated/index.htm
Manual on the Use of Self-Propelled Modular Transporters to Remove and Replace
Bridges. Report No. FHWA-HIF-07-022. FHWA, U.S. Department of Transportation,
Washington, DC. June 2007. Accessible at http://www.fhwa.dot.gov/bridge/pubs/07022/
Developed By:
The Roadway Safety Consortium
202-628-5465
www.workzonesafety.org
Laborers’ International Union of North America
Laborers’ Health and Safety Fund of North America
LIUNA Training and Education Fund
American Road and Transportation Builders Association
National Asphalt Pavement Association
International Union of Operating Engineers
American Association of State Highway and Transportation Officials
Texas Transportation Institute
FOF Communications
U.S. Department of Transportation Federal Highway Administration
U.S. Department of Transportation Federal Highway AdministrationThis material is based upon work supported by the Federal Highway Administration under Grant Agreement No. DTFH61‐06‐G‐00007.
Any opinions, findings and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the Federal Highway Administration. This publication does not constitute a national standard, specification or regulation.
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