Assessing Heavy Vehicle Impacts on Operation of Rural At-Grade Intersections in Brazil

Abstract

A simulation model was used to assess the impacts of trucks on the capacity of rural, at-grade, stop-controlled intersections in Brazil. The major differences between Brazilian and North American vehicles and intersections are discussed and a system for vehicle classification that reflects the characteristics of Brazilian vehicles is proposed. The proposed simulation model assumes that there is an endless queue of vehicles that approaches the intersection from the minor road. Gaps in the major road traffic flow are generated using a displaced exponential distribution. Crossing times and gap acceptance are modeled by logit models fitted for each vehicle category. Heavy vehicle equivalence factors are calculated as the average number of passenger cars that are able to cross the major road during the time required by each truck type to execute the same maneuver. The capacity estimates obtained with the model are similar to values calculated with Siegloch's model, which is the basis for the Highway Capacity Manual (HCM) procedure. The equivalence factors estimated for trucks are considerably higher than those suggested in the HCM for most truck categories.