Gap‐Acceptance Problems at a Traffic Intersection

A driver who is waiting at a give way sign on a minor road and who wishes to turn into the major‐road stream is faced with a series of gaps on the size of which he must base his decision to cross. This paper reviews the problems involved in the collection and analysis of accepted and rejected gaps, and illustrates them with data from a particular location. The results of such analyses can have important implications for road safety. Not all the problems associated with the analysis of gap‐acceptance data have been solved. These problems centre round getting satisfactory tests for the differences between parameter estimates. Non‐parametric tests can play a part, as also can probit analysis, but not all the difficulties have been overcome. The data used in this paper show no real evidence that the impatience of drivers stopped at an intersection increases with the time they have to wait—a result of possible psychological importance. All the parameters considered gave the same indication that longer gaps are required for the right‐turn manœuvre. These gaps were only about half as long in the rush‐hour. The difference between normal and rush‐hour flow for left‐turning and through traffic was much less marked. This result may be thought to conflict to some extent with the finding of the previous paragraph, but overall there was no evidence that undue risks were being taken.