Macrotexture and crash risk : some recent findings from Australia and their implications.

The importance of road surfacing for good safety performance has been understood from the earliest days of motorised transport. Laser profilometers offer new ways of assessing road surfaces but little has been done to match this information to the crash histories of roads. Macrotexture, defined as surface irregularities between 0.5 mm and 50 mm in height, seems particularly promising as an indicator of satisfactory road surface on high speed roads. This paper briefly reviews previous work and reports two new Australian studies which broadly confirm the results of the earlier work, i.e. that crash risk increases considerably once macrotexture falls below a threshold level. The implications of the findings for the management of road surfacing is explored, along with the implications for the assessment and management of road surfaces. Among the issues considered are how well macrotexture predicts high-risk locations compared to current skid resistance measures, high-risk situations that may not be detected by macrotexture alone, and the research required before the feasibility of a surface management regime based principally on macrotexture could be assessed. (a) For the covering entry of this conference, please see ITRD abstract no. 0612AR242E.