Traffic conflicts as crash surrogates

Abstract A traffic conflict is defined as etiologically connected to a crash through a failure that causes the conflict, and the inevitability of crash if a correction is not made. Other definitions of conflict proposed over the years include the presence of failure-free aggressive behaviors. The proposed modification strengthens the causal relationship between conflict and crash as understood in the light of counterfactual analysis and Pearl's work on causality. Measures of crash nearness discussed in this chapter include time to collision, instantaneous time to collision, and post-encroachment time. A small separation between road users moving along conflicting paths and the necessity of an evasive maneuver are conditions for a traffic event to be a conflict.