Resumen
The sun is most hazardous to drivers when it is close to the horizon, particularly within an hour after sunrise (dawn) and an hour before sunset (dusk). The position of the sun and the angle of the rays during this period can render sun visors inadequate, thus increasing the risk of accidents by interfering with a driver?s ability to see the road ahead. This paper describes a GIS-based methodology to determine direct sunlight exposure (sun glare) for the road network in Cape Town. For an arbitrary position in the roadway alignment of the study area, the amount of sun glare risk for drivers, resulting from vision impairment, was analysed for the 2014 equinox and solstice days. Each of these astronomical events occur twice a year and have the added benefit of seasonal variation. The results of the study revealed that about 14.7% of the Cape Town road network in the autumnal equinox and spring equinox is exposed to direct sunlight while 12.2% and 15.2% is exposed in the winter solstice and summer solstice, respectively. Moreover, a case study carried out in one of the Cape Town streets provided a validation of the methodology and proved the reliability of the results. Therefore, data analysis results obtained using this methodology can be an important factor to consider when evaluating existing roads or layout and alignment alternatives for new roads. This methodology can also be incorporated into car navigation systems and variable message signs to provide automated real-time sun glare risk information to drivers.