Spatiotemporal Patterns of Primary and Secondary Incidents on Urban Freeways

Abstract

Incidents on urban freeways are a leading cause of traffic congestion. Secondary incidents can occur in the vicinity of primary incidents, complicating traffic operations. While studies have examined factors associated with incident duration and secondary incident occurrence, a significant number of spatiotemporal variables in incident management are often overlooked. For example, how soon does a secondary incident happen after a primary incident? How far is the secondary from the primary incident? What factors are associated with near versus far secondary incidents? To answer these questions, a deeper analysis of primary and secondary incidents was conducted on the basis of a unique 2008 incident and roadway inventory database for Hampton Roads, Virginia. Time gaps and distances for secondary incidents in the same direction were analyzed with appropriate statistical methods. This research contributes to incident management by rigorously analyzing time-gap distances between primary and secondary incidents and exploring their implications. The results can support more informed planning and operational decisions needed to respond in complex incident situations.