A methodology to assess the road accident risk as a result of direct sunlight exposure : a case study in Cape Town

Abstract

The sun is most hazardous to drivers when it is close to the horizon, particularly within an hour time frame after sunrise (dawn) and before sunset (dusk). The position of the sun and the angle of the rays during this period can render sun visors inadequate. As a result, the risk of having an accident is increased, due to the interference with a driver?s ability to see the road ahead. This paper discusses a Geographic Information Systems-based methodology, which was used to determine the areas of the City of Cape Town road network that are exposed to direct sunlight (sun glare); thus creating a road safety risk. For an arbitrary position in the roadway alignment of the study area, the amount of sun glare risk for drivers was analysed for the 2014 equinox and solstice days. The results revealed that approximately 14.7% of the road network in the autumnal equinox and spring equinox is exposed to direct sunlight (sun glare risk), while 12.2% and 15.2% are exposed in the winter solstice and summer solstice, respectively. A case study carried out in one of the Cape Town streets proved that the methodology produces valid and reliable results. Therefore, results from this procedure can be an informative dimension to consider when evaluating existing roads or layout and alignment alternatives for new roads. In addition, the methodology can also be incorporated into car navigation systems to provide automated real-time sun glare risk information to drivers.