Visibility improvements through information provision regarding sun glare : a case study in Cape Town
Master Thesis
2014
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University of Cape Town
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Abstract
Vision is inarguably a fundamental component of safe driving. Any obscurity in a driver’s vision can impose a threat to roadway safety due to interference with the driving task. Sun Glare is a hazard that few people anticipate. The sun is most potent to drivers when it is low in the sky on the horizon, particularly an hour or so after sunrise (dawn) and before sunset (dusk). The position of the sun and the angle of the rays during this period may render sun visors useless. This increases the risk of an accident as a result of interference with a driver’s ability to see the road ahead. The primary purpose of this study was to develop a method which will determine which areas in the City of Cape Town road network are exposed to direct sunlight, thus, making them vulnerable to road accident risk as a result of impaired vision. Additional objectives included the validation of the methodology by comparing field investigation outcomes with those of the established methodology. Considering the need for a tool with the ability to combine spatial data and sun position data, the ArcGIS software, which contains the hillshade tool, was selected for use in the study. The study was conducted for the City of Cape Town road network. The data used in the investigation included a Digital Elevation Model (DEM) and road network data of the study area. The DEM and road network data were both derived from a 10m topographical map. Sun position data (azimuth and altitude) was obtained from the Astronomical Applications Department of the U.S. Naval Observatory server. The sun position data obtained was for the morning and afternoon period of four days chosen for usage in the development of the model: Autumnal Equinox (AE), Spring Equinox (SE), Summer Solstice (SS) and Winter Solstice (WS). A 19º-25º altitude sun cone and a ±15º threshold (azimuth sun cone) were adopted for the filtering of road segment azimuth and slope. The field investigation carried out to validate the model was executed using a Road Eye JS-300 camera.
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Khumalo, N. 2014. Visibility improvements through information provision regarding sun glare : a case study in Cape Town. University of Cape Town.