Assessing the Occlusion Effect of Large-Dimension Vehicles on Traffic Signs at Multilane Highways

Abstract

This paper presents an investigation into the different factors that affect sign occlusion by large-dimension vehicles on multilane highway facilities. Parametric analyses were conducted to explore these effects using a simulation model that was developed specifically for this research. The variables investigated involved legibility distance, maximum divergence angle, average speed of passenger cars, relative speed of trucks with respect to passenger cars, lateral offset of traffic sign, number of words in message, traffic level, and percentage of large-dimension vehicles. In general, research results show that the occlusion of ground-mounted traffic signs by larger vehicles is remarkable for conditions that can be described as typical. Also, results suggest that the factors that have most important effect on sign occlusion involve legibility distance, average speed of passenger cars, relative speed of trucks with respect to passenger cars, and number of trucks on the lane of interest.