Relationship between texture depth and collision risk on the Strategic Road Network

Road surface friction on the Strategic Road Network (SRN) is managed through the requirement to provide appropriate levels of skid resistance and texture depth. Th relationship between skid resistance and collision risk has been established in previous studies; this study focussed on the relationship between collision risk and in-service texture depth as measured by routine network surveys, i.e. laser based measurements of Sensor Measured Texture Depth (SMTD). The results showed that there was a general trend for collision rate to increase with decreasing texture depth, but that this increase was associated mainly with collisions in dry conditions; however, measurements show that dry friction does not appear to vary with texture depth. Therefore, further investigation is recommended to develop a better understanding of other factors that could be contributing to the increase in collision risk such as collision type, contributary factors or human factors. This understanding would then enable strategies to be developed to mitigate the increased risk.