IMPROVING THE CAPACITY OF RURAL ROADS. 24TH ARRB REGIONAL SYMPOSIUM, BUNDABERG, QUEENSLAND, AUSTRALIA, 1986

The 1985 highway capacity manual represents the current state of the art in assessing the performance of roads. The section dealing with two lane roads is based on earlier manuals but includes a number of new parameters including a platooning term (per cent of time delay) and a different technique for estimating the level of service and the capacity on selected grades. This paper discusses the history of the section of the 1985 highway capacity manual which deals with two lane rural roads by tracing the approach used in previous manuals and noting the differences. Relevant Australian research and its implications to the design of rural roads are also discussed. It is concluded that the addition of an overtaking lane can have a significant effect on the service volume of the road. Other techniques like increasing the lane width or shoulder width have only a minimal effect on the performance of the road. It is also concluded that many of the new features in the 1985 highway capacity manual have been proposed by Australians and there is a need to continue our research in this area. (TRRL/Authhor)