Abstract
It has been shown that accident rates tend to increase sharply with average daily traffic (ADT). Whether the levels of service which are being increasingly used to describe highway operation are related to the accident rate is unknown. Definition of this relationship might provide a useful method to predict future operational effectiveness of roadway designs. As better and more uniform accident, flow, highway, and environmental data become available, generally applicable relationships can be developed. Most of the work to date has been for rural highways.