Improving Roadway Operations and Safety for Large Truck Vehicles by Optimizing some Critical Geometric Design Parameters

Abstract

Large truck vehicles are constrained by their physical and operational attributes such as length, width, height and axle loading, which affect their performance on highway infrastructure. In recent times, car-truck and truck only crashes have increased due to the complex interactions of such vehicles on geometrically deficient roadway systems. By adjusting geometric design parameters in accordance with stipulated requirements across deficient roadway sections it is possible to estimate using crash rate index the degree of improvements observed. A total of 189.4 kilometers of three roadway lengths (Benin-Ore, Benin-Agbor and Benin-Sapele) were investigated for geometric design deficiencies across crash sections. Adjustments were made using AAHSTO design specifications based on speed limit, terrain type and roadway functional class for three critical geometric design parameters namely: degree of horizontal curvature, vertical grade and roadway lane width. Comparison of parameter estimates before and after adjustments showed corresponding cumulative percentage improvements of 6.5%, 13% and 4.7% for Benin-Ore, Benin-Agbor and Benin-Sapele roadways respectively. This implies that adjustments to critical design parameters at deficient roadway sections can help in mitigating large truck crash rates and allow for better accommodation and operation of such truck vehicles on plied roadways.