GAP ACCEPTANCE: MYTH AND REALITY

Three general models of driver gap acceptance behaviour are discussed. They are: a) a fixed critical gap, b) consistent individual drivers, and c) inconsistent individual drivers. The limitations and implications of the models and the restrictions imposed by the nature of the data are discussed. The model in which each driver has a constant critical gap, distributed over the population, is closely examined, and it is concluded that the distribution of critical gaps cannot be estimated from data available from field observations. It is suggested that use of the distribution of observed accepted lags (or gaps) together with conditional probabilities of acceptance should be used in comparison studies. Truncated normal and Weibull distributions have been successfully fitted to empirical data on accepted lags and gaps. For the covering abstract of the symposium see TRIS 452544. (Author/TRRL)