Managing road surfaces for safety at the network level: is macrotexture enough?

This paper reports an analysis of the relationship between road surface characteristics and crashes on undivided two-way roads in the state of Victoria, Australia. Surface condition data from multi-laser profilometer surveys was linked to geometry, traffic and crash data using GIS and the resulting tables analysed to investigate the relationships. The three road surface characteristics were either uncorrelated or showed small enough correlations to disregard possible interactions among the variables. Crash rate was higher for road sections with low macrotexture; a power relationship provided a good fit to the data. Crash rate was also higher for roads where roughness was extreme, with a polynomial relationship providing a good fit to the data. No clear relationship emerged between rutting and crash rate. An economic analysis suggests that resurfacing sites with macrotexture of 1 mm SPTD or less would produce crash savings which would provide a very good return on the investment.