This investigation aimed to describe the distribution of surface characteristics (i.e. macrotexture, rutting and roughness, with the addition of skid resistance (SFC) for the urban network) and the relationship between them, and the relationship of surface characteristics to crash occurrence. The investigation also examined how geometry affected the relationship between surface characteristics and crashes. Additional analysis is carried out to investigate the relationship between macrotexture and crash occurrence in detail, to test the sensitivity of the lengths of section used in the analysis, and to check whether crash occurrence can be related to surface characteristics some distance before the crash site. Data were obtained for a Victorian urban network, a Victorian rural network, and a WA rural network. The crash data covered a five year period; road surface condition data were taken from multi-laser profilometer or SCRIM surveys which were conducted near the middle of the study period; traffic data were the figures estimated by the road authority for the purposes of the Auslink program. A robust relationship was found between crash rate and macrotexture on Victorian rural roads which agrees well with previous findings from Australia and overseas, although recent New Zealand work found no relationship. Wet weather crashes were not over-represented at low macrotexture sites, but multi-vehicle crashes were. A linear relationship was found for crash rate and roughness; these results agree well with recent work from both New Zealand and Sweden despite differences in crash definitions, road systems and climate. These findings were not replicated on Victorian urban roads, nor on WA rural roads. The reasons for the non-replications are discussed. (Author/publisher)
Abstract