The safety impact of road lighting on roads with speed limits greater than 70km/h

This paper reports a project to improve understanding of how road lighting quality influences night-time crashes in higher speed limit areas on the urban fringe. The work complements previous urban work by the same authors. The study featured generalised linear modelling and illustrated relationships between crashes and CIE lighting parameters using two dimensional plots. It considered three road types: motorways, median divided highways and single carriageway roads. There was no evidence that lighting motorways to levels above the current 0.75 cd/m2 design level improved safety. Increasing the overall uniformity for Uo values up to 0.4 showed improved safety, but no safety relationship was found for longitudinal uniformity. Single vehicle lost control crashes appeared little influenced by the presence of lighting. Rear end crashes were strongly reduced by lighting. Crash reductions were generally greater for more serious crashes. The study concluded that the largest lighting-related crash reductions occur for motorways, arising principally from a reduction in rear end crashes. Estimates of the crash savings associated with lighting for all three road types considered were made. As most of the roads considered were motorways, results for other road types relied on a relatively small sample and should be considered exploratory.