Work Zone Mobility and Safety Program

Executive Summary

Congestion and safety issues often arise in and around work zones as agencies work to implement necessary construction and maintenance projects. Degraded facilities, narrowed lanes, and lane restrictions often result in unpredictable, unstable traffic flow. With recent efforts to focus on improving work zone operations, including the recently implemented Work Zone Safety and Mobility Rule, state Departments of Transportation (DOTs) are looking for tools and applications that will improve mobility and safety by actively managing traffic through the work zone. Intelligent Transportation System (ITS) applications are one tool that agencies are using to try to mitigate traffic impacts caused by construction.

The purpose of this study was to perform 'before and after' analyses to quantify the mobility and safety benefits of using ITS applications for work zone traffic management. A number of states have used ITS for work zone traffic management, and these systems often take the form of portable traffic monitoring and management. Work zone ITS systems provide information to motorists to help with route choice. These systems also provide advance warning of slowed or stopped traffic, which prepares motorists to respond to traffic conditions ahead and eases frustration for motorists who do not know what to expect. Work zone ITS also can be used to manage merging approaching lane closures and for speed management. As both the number of work zones and the use of ITS technology to monitor and manage traffic through the work zone increases, more information is needed on the quantified benefits of use as well as the lessons learned by agencies that have tested and implemented these systems. This information will lead to more effective implementations and allow agencies to learn from the past experiences of others.

The study focused on sites that provided an opportunity for comparison of traffic conditions both with and without ITS. The study team focused on sites with the best potential for adequate data prior to system deployment (and with impacts from construction), for comparison with traffic conditions during system deployment.

The study team evaluated ITS systems from sites in North Carolina, Arkansas, Michigan, Texas, and the District of Columbia. For some of the sites it proved difficult to determine quantifiable benefits due to issues with both deployment schedule and implementing data collection plans due to varying construction schedules. However, some key lessons learned and benefits were discovered from each site using work zone ITS. Some key benefits include:

  • Reductions in aggressive maneuvers at work zone lane drops (Michigan) - Forced merges were 7 times less frequent, and dangerous merges were 3 times less frequent when the ITS system was on (flashers on).
  • Significant traffic diversion rates (Texas, District of Columbia) in response to appropriate messages displayed during congested conditions, and an enhanced ability to manage traffic and incidents during construction. In Texas, an average of 10 percent diversion (range of 1 to 28 percent) was observed, while in the District of Columbia an average of 52 percent (range of 3 to 90 percent) lower mainline volume (combination of diversion, demand reduction, and congestion) was observed.
  • Improved ability to react to stopped or slow traffic (Arkansas) - 82 percent of surveyed drivers felt that the ITS system improved their ability to react to stopped or slow traffic.
  • Driver perception of improved work zone safety (Arkansas) - 49 percent of surveyed drivers indicated that that the ITS electronic messages made them feel safer. 17 percent were neutral, 32 percent disagreed, and 2 percent did not answer.

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