ABSTRACT
As one of the main elements of geometric design, sight distance must be considered carefully for the safe and efficient operation of highways. An application developed on Geographic Information Systems (GIS) was conceived for the three-dimensional estimation of sight distance on highways, as opposed to conventional two-dimensional techniques, which may underestimate or overestimate the actual visibility conditions. It is capable of computing the available sight distance of a highway section given the driver’s eye height, the target height, the vehicle path and an elevation model. The outcome can be studied in detail with the aid of the tools and capabilities developed, including sight-distance graphs. The influence of the input features, such as the nature of the elevation model, its resolution and the spacing between path stations on the results accuracy was analyzed. The interpretation of results is also essential to explain sight distance deficiencies and provide insight into the effect of roadside elements on those results. In addition, the sight-distance graph permits the detection and characterization of sight-hidden dips, an undesirable shortcoming in the spatial alignment of highways. The versatility of GIS enables, moreover, an integrated research of highway safety. It allows the incorporation of diverse operational factors such as accident data, traffic volume, operating speed and design consistency to detect and diagnose potentially hazardous spots or, eventually, identify the factors involved in a particular accident. This paper describes the methodology utilized and reviews the main issues through case study examples.
