Incident Diversionary Routing: Survey of Influences and Decisions

Abstract

When confronted with congestion and delay, drivers often divert their route. Depending on factors like purpose, urgency, destination, route alternatives, type of disruption, and mode options, common diversionary options can range from changing departure time, route, and mode to canceling a trip altogether. The choice to divert depends on several factors, including whether, when, and where they become aware of a disruption. As the ability of transportation agencies to detect incidents, inform drivers of conditions, and implement control-changes to accommodate volume surges has improved, there is increasing interest in knowing whether drivers will divert and why. This article describes the results of research using marketing-based survey techniques to evaluate driver diversionary behavior during roadway incidents. The survey was used to identify and assess diversionary choice-making a) based on travel behaviors and habits, b) under routine and adverse conditions, c) for different incidents and route options; and d) under varied guidance information available to them. The results showed that travel time reduction was the primary motivator for alternate path use to avoid congestion, consistent with previous research. Interestingly, younger males showed the lowest level of influence from guidance information, and route familiarity had a lower influence on diversionary routing among all groups, suggesting a trust in real-time mobile routing guidance. With additional analyses, these findings could be applied to estimate and model driver actions under a range of driver-, network-, travel-, and disruption conditions.