This paper describes part of a study of the effect of overtaking provision on operating speed and capacity on single carriageway roads. The objective was to update and extend previous studies and to allow the influence of alignment and sight distance to be re-assessed. More than 1100 overtaking manoeuvres were recorded using a series of three video cameras to cover a 1km length of overtaking section. Overtaking behaviour variables which include the decision time, the duration of, and distance travelled during the overtaking manoeuvre, safety margins, headways at the start and finish of overtaking and the accepted gaps were measured using a microcomputer based data logging system to extract data from video recordings. The relationship between variables has been examined and appropriate distributions have been fitted. Formulae have been developed in which each variable may be estimated, for different types of overtaking manoeuvre, based on the speed of the overtaken vehicle and the accepted gap size. The results of the study are compared with previous research both in the U.K. and overseas. (A)
Abstract