NEW MODEL FOR PREDICTING FREEWAY INCIDENTS AND INCIDENT DELAYS

This paper presents a new model that predicts the number of freeway in cidents and associated delays based on general freeway segment charact eristics, traffic volumes, and incident management procedures. The mod el is intended to be used in planning capacity-enhancing freeway impro vements and incident management programs. Estimates of incident freque ncies, severity, durations, and delays are provided for seven standard incident types, each of which represents a significant fraction of to tal unplanned incidents and has severity and/or duration characteristi cs substantially different from the others. In addition to describing the incident prediction model, the paper addresses the need for a coor dinated national strategy for collecting incident data, with particula r attention to urban freeways. It concludes that the incident data sys tems that have evolved in several urban areas, often in connection wit h freeway service patrols and incident response team activities, alrea dy provide a valuable nationwide data resource for understanding incid ent patterns and their variations. However, better national coordinati on of locally collected incident data would be helpful for addressing issues beyond the scope of the local concerns for which virtually all current systems were originally designed. Specific areas for improveme nt include the definitions of incident types, descriptions of incident locations (relative to both the length and breadth of the highway), a nd data recording the critical times during incidents such as when det ection, response, and clearing occur.