Impact of Abandoned and Disabled Vehicles on Freeway Incident Duration

Abstract

It is common to find a vehicle left on the shoulder, median, gore area, or on the travel lane for certain period of time. Experience from the state of Tennessee has shown that 78% of the freeway traffic-related incidents are attributable to disabled and abandoned vehicles. It is hypothesized that the longer the vehicle is left unattended within the right of way, the higher the probability of new incidents and secondary crashes. This paper utilized 2004–2010 freeway incident data in Tennessee to evaluate the effect of the length of incident durations caused by disabled and abandoned vehicles. Analysis evaluated the effect of these incidents with respect to roadway location, queue lengths, weather conditions, towing times, lane closure, and the source of incident notification. Temporal factors, including the spectra of the time of the day, the day of the week, and the seasons of the year were evaluated with respect to the number of incidents and incident durations. More disabled and abandoned vehicles were located in the left and right shoulders than in other cross-sectional positions of the roadway. Parametric hazard-based log-logistic survival model was applied to determine factors affecting abandoned and disabled vehicles incident duration. The number of closed lanes, length of the queue formed, construction zones, trucks, and towing involvement were found to be significantly associated with longer incident duration. Some of the recommendations included the expansion of the use of the highway emergency local patrol (HELP) program as the incident notifications received through it were more precise, leading to fast clearance of incidents.