Solar glare vulnerability analysis of urban road networks—A methodology

Abstract

Solar glare on roads is responsible for momentaneous deterioration of a driver’s view, interfering with driving capacity and causing accidents. The situation of a driver being affected by solar glare on a road is a spatial-temporal variable, since it depends not only on the time of the day and the day of the year, which are determinant for the local Sun position (temporal factors), but also on the local slope and azimuth of the road in the driven direction (spatial factors). The present work describes a method for producing road glare maps along a road network, as well as retrieving glare information from urban roads so that solar glare vulnerability can be easily accessed. Input data are a 1m resolution Digital Surface Model from Light Detection and Ranging data and the road network. Spatial parameters are processed in a Geographic Information System environment. The Urban Glare Algorithm detects glare and outputs temporal matrices and glare maps. Shadows cast by buildings and trees are considered as well as the driver’s eyes height. The method is tested in an area of Lisbon (Portugal). This work is a contribution to road safety systems implementation and constitutes a relevant basis for warning drivers of glare through car navigation systems.