PERFORMANCE CHARACTERISTICS OF COAL-HAULING TRUCKS IN MOUNTAINOUS TERRAIN

Objectives of the study were to analyze and evaluate speed characteristics of coal trucks on two-lane mountain highways and to identify and quantify traffic performance limitations related to heavy trucks. To accomplish these objectives, spot speed data were collected on three coal-haul roads in West Virginia and a simulation analysis was performed by using the geometric characteristics of the same three sites as input. Upgrade and downgrade speed profiles were plotted for passenger cars and three classes of trucks. Truck speeds were significantly lower than passenger-car speeds on upgrades. On downgrades, the speed difference was not so pronounced and depended on whether trucks used braking or lower gears to reduce speed. Although simulated truck speeds showed good agreement with field data, simulated passenger-car speeds were uniformly higher than field speeds. This was attributed to the narrow roadway and rough pavement condition of the study sites. Geometric delay was significantly greater than traffic delay. Both types of delay were quantified for a variety of geometric and flow conditions. Acceleration noise, another traffic-flow parameter, was used as a measure of accident potential and stability of flows. Acceleration noise increased as volume increased on both upgrades and downgrades. Upgrade acceleration noise was greater than downgrade noise. Several practical applications of the results and directions for future research were presented. (Author)