Cost of Congestion Due to Incidents on Freeways

When alternative incident management strategies are evaluated, there is often a need to convert reductions in incident clearance time to a monetary cost saving. In the past, the Virginia Department of Transportation (VDOT) has used unit delay costs from other agencies to estimate incident congestion costs and the benefit of incident management programs. To improve current practices, congestion cost values developed specifically for Virginia conditions are desired. This study developed a method to produce planning-level incident congestion cost estimates for interstate highways in Virginia. The per-minute incident congestion costs were estimated using economic, traffic, incident, and roadway data from multiple sources and analyzed at different spatial and temporal aggregation levels. The results showed that the proposed method can produce reasonable estimates of congestion cost at a planning level. The incident congestion costs vary across VDOT districts, routes, time-of-day, and day-of-week; the costs can vary from less than $1 per incident-minute for shoulder-closed incidents in the Bristol District during off-peak hours to $1,347 per minute for lane-blocking incidents in the Northern Virginia District during AM peak hours. With the variation in costs, the study recommends that corridor-based cost values (where “corridor” is defined as a directional route within a district) be used for analyses of projects across different locations and time periods. The study also recommends that VDOT develop a plan to maintain and update congestion cost values and develop a field-ready App to provide easy access to the congestion cost values for VDOT staff. The full report is available from the VDOT web site at https://www.virginiadot.org/vtrc/main/online_reports/pdf/22-R15.pdf