Considerations for the Development of Work Zone Mobility Performance Measures and Thresholds for Virginia Freeways

The Federal Highway Administration has been encouraging states to improve their monitoring and tracking of the mobility impacts of work zones. The use of mobility performance measures will enable agencies to assess better the contribution of work zones to network congestion; to identify specific projects that are in need of remedial action; and potentially to assess penalties to contractors creating excessive, avoidable negative impacts. Although the Virginia Department of Transportation (VDOT) has defined allowable lane closure hours for the interstate system, VDOT has not defined specific performance measures and thresholds for what constitutes “unacceptable” work zone mobility impacts. Performance measures and thresholds have been developed by a number of other states, so there is a need to determine whether these could be adapted for use by VDOT. This study explored issues related to a potential work zone mobility performance measurement program for Virginia. The issues investigated included identification of potential performance measures, definition of performance thresholds, and recommendations for data sources for performance measurement calculations. This information was synthesized from information regarding the experiences of selected states and experiences from a series of case studies that used data from Virginia work zones. The review of experiences in selected other states found that delay and queue length were the performance measures used most often by the states studied. The Virginia case studies focused on the use of private sector data to generate mobility performance measures and found that the level of spatial aggregation in rural areas could inhibit the ability to generate accurate performance measures, although granularity was better on urban roads. The level of temporal aggregation was also found to influence performance measures. The research identified a number of key issues that VDOT should consider as a work zone mobility performance measures program is developed. The report recommends that VDOT develop a pilot program that focuses on urban interstates initially and convene a task group to develop formal policies and procedures for use in the state.