Exposure effects on the rate and severity of highway collisions at different travel speeds.

This memorandum develops a simple description, or model, of the accident rates of vehicles travelling at various speeds on a highway. Comparisons with available observational data show that the model correctly reproduces the observed forms of function relating accident rate to speed of travel for collisions between vehicles travelling in the same, or opposing, directions. An extension of the model to estimate the travel speed differentials between colliding pairs of vehicles travelling in the same direction showed poor agreement with observations.