OVERTAKING BEHAVIOUR ON NARROW TWO-LANE TWO WAY RURAL ROADS

Overtaking data were collected on two roads with pavement widths of 7.4 and 6.0 m. Both roads were located in rural parts of eastern Victoria. The experiment technique was to observe and record the behaviour using a video recorder and to digitally log information onto the screen. It was concluded that the mean overtaking time was increased from 8.6 to 9.3 s and that the 85th percentile overtaking time was increased by 18 per cent on the narrow roads. This caused an increase in the calculated establishment sight distance of 12 per cent. Mean safety margins were unaffected. The difference in the behaviour of motorists during various sections of the manoeuvre were also discussed in this report. The principal conclusion is that a decrease in pavement widths substantially affects the level of service of a two-lane rural road at moderate traffic volumes. For example, for a flow of 600 veh/h, the overtaking frequency is about half that on wider 7.4 m roads. (Author/TRRL)