This report presents the results of a Federal Highway Administration study that examined the use of Intelligent Transportation Systems (ITS) for work zone traffic management. 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 that focus on improving work zone operations, including the recently implemented Work Zone Safety and Mobility Rule, State Departments of Transportation (DOTs) are looking to tools and applications that can help improve mobility and safety by actively managing traffic through the work zone. ITS applications are one tool that agencies can use to mitigate traffic impacts caused by construction.
A number of states have used ITS for work zone traffic management. These systems often take the form of mobile, portable traffic monitoring and management to provide information to motorists to help with route choice, provide advance warning of slowed or stopped traffic, and overall to ease frustration due to not knowing what to expect. To promote further use of ITS technology to monitor and manage traffic through the work zone, more information is needed on the quantified benefits of use and the lessons learned by agencies that have tested and implemented these systems.
The purpose of this study is to highlight "before and after" or "with and without" analyses that quantify the mobility and safety benefits of using ITS applications for work zone traffic management. 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. Five sites were assessed for this study. This study also examined findings from other work zone ITS research as compared with the findings presented from the five study sites.
The study team analyzed data from sites in the District of Columbia, Texas, Michigan, Arkansas, and North Carolina. For some of the sites, it was difficult to determine quantifiable benefits due to issues with deployment schedule and difficulties in implementing data collection plans due to varying construction schedules. Other sites showed clear, quantified benefits. Some key lessons learned that can help deploying agencies are presented for all sites. Additionally, quantitative benefits information is included for several sites, such as:
- Reductions in aggressive maneuvers at work zone lane drops (Michigan) – Forced merges were seven times less frequent and dangerous merges were three times less frequent when the ITS system was on (flashers on).
- Significant traffic diversion rates and lower observed mainline volumes (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.