TRAFFIC OPERATION ON BUSY TWO-LANE RURAL ROADS IN THE NETHERLANDS

In the framework of updating standards for describing the quality of traffic flow on two-lane rural roads, research into the behavior of the traffic flow on relatively high-volume roads was carried out. Presented in this paper are findings about the relation between the volume and traffic composition as explanatory factors for speeds, headways, and platooning. It was found that mean speed was only marginally influenced by volume and truck percentage, whereas the standard deviation of speeds decreased substantially with increasing volume. An exponential tail model for headways, large enough to be relevant for passing opportunities, was used and its parameters were successfully related to volume. This model fits reality much better than the assumption that headways have a negative exponential distribution, which leads to severe underestimation of passing opportunities. Simple models were developed that relate the proportion of vehicles following in a platoon and the maximum platoon length in 5 min to volume and truck percentage. A comparison is made with results in the proposed Chapter 8 on Two-Lane Highways of the 1985 Highway Capacity Manual.