Definitions are given for the various types of traffic conflicts, erratic maneuvers, and near-miss accidents. The General Motors technique for observation of traffic conflicts is summarized. Procedures used by several highway agencies for collecting conflict data are also detailed. Criteria which have been used to identify hazardous intersections using traffic conflict data are summarized. Methods and examples of evaluating safety improvements are detailed. Relationships between conflicts and accidents found by others were given.

The procedure for observing traffic conflicts on freeway ramps is described. Definitions are given for erratic maneuvers at lane drops, gore areas, and intersections. Results from studies which utilized counts of erratic vehicle maneuvers are mentioned. The concept of near-miss accidents and the time-to-accident concept, as currently used, are explained. Advantages and limitations are given for the use of conflicts, erratic maneuvers, and near-miss accidents in identifying hazardous sites and evaluating safety improvements.

Report Date


Report Number

No. 484

Digital Object Identifier



The contents of this report reflect the views of the author who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Bureau of Highways. This report does not constitute a standard, specification, or regulation.