The work reported in this paper arose from a need to improve the speed prediction algorithms embedded in the Australian non urban road planning models. It summarises work carried out to determine the effect of variations in surface roughness and road width on free running speeds on sealed and gravel two way two lane rural highways and roads in New South Wales and Queensland. Effects of other variables including alignment and traffic were controlled via careful site selection, survey timing, and data analysis. Speed surveys of 24 or more hours duration were carried out at 27 sites on the Newell Highway and an adjoining road in New South Wales; and at 42 sites on gravel and formed roads in the vicinity roads in the vicinity of Roma and Gympie in Queensland. In subsequent analysis, speed was shown to have statistically significant correlations with roughness and to a lesser extent with road width, with effects varying between vehicle classes and road surface types. Differences between survey results and relationships assumed in existing models were observed indicating a need to modify the latter. (A)
Samenvatting