Useful estimation procedures for critical gaps

Many different methods for the estimation of critical gaps at unsignalized intersections have been published in the international literature. This pap er gives an overview of some of the more important methods. These methods a re described by their characteristic properties. For comparison purposes a set of quality criteria has been formulated by which the usefulness of the different methods can be assessed. Among these one aspect seems to be of pr imary importance. This is the objective that the results of the estimation process should not depend on the traffic volume on the major street during the time of observation. Only if this condition is fulfilled, can the estim ation be applied under all undersaturated traffic conditions at unsignalize d intersections. To test the qualification of some of the estimation method s under this criterion, a series of comprehensive simulations has been perf ormed. As a result, the maximum likelihood procedure (as it has been descri bed by Troutbeck) and the method developed by Hewitt can be recommended for practical application. (C) 1999 Elsevier Science Ltd. All rights reserved.