Evaluation of GIS Applications for Horizontal Curve Data Collection

Abstract

Applications that use a geographic information system (GIS) are common and useful in the field of transportation. Horizontal curves are critical components on a roadway in their role as a transition between straight segments and in their potential as a safety hazard to motorists. Therefore, determining the characteristics of curves [both spatial (including location, length, radius) and nonspatial (including traffic volume, signage, pavement type)] is an important task. GIS applications have been developed for evaluating roadway alignments in general and some have focused on horizontal curve assessment. This paper reports on two benchmarking efforts. The first assessed and established the accuracy of three publicly available GIS applications for determining curve spatial characteristics. The second assessed the quality of available GIS roadway line work. The three GIS applications were evaluated for performance accuracy on the basis of a comparison with precisely drawn curves [with radii ranging from 30.5 to 1,524 m (100 to 5,000 ft)]. The line work was evaluated on the basis of a comparison with field measurements from 51 curves [with radii ranging from 61.6 to 1,832.2 m (202 to 6,011 ft)]. The analysis found that the use of a GIS to accurately determine horizontal curve radius and length is possible. The Curvature Extension GIS application is recommended for individual curve analysis while Curve Calculator can produce sufficient results for individual curves if a substantial number of GIS points exist (8 points for an error of approximately 1% and 25 GIS points for an error of less than 0.1%). For network or route analysis, Curve Finder is recommended. This paper presents the methodology and analysis that led to these findings.