Downgrade Speed Characteristics of Heavy Vehicles

by Abishai Polus, (M.ASCE), Lect. of Civ. Engrg.; Dept. of Civ. Engrg., Technion—Israel Inst. of Tech., Haifa, Israel; currently Visiting Assoc. Prof., Dept. of Civ. Engrg., West Virginia Univ., Morgantown, W. Va. 26506,
Izhak Grinberg, Research Engr.; Dept. of Civ. Engrg., Technion—Israel Inst. of Tech., Haifa, Israel,
Joseph Craus, Prof. of Civ. Engrg. and Head of Transportation Research Inst.; Technion—Israel Inst. of Tech., Haifa, Israel,

Serial Information: Transportation Engineering Journal of ASCE, 1981, Vol. 107, Issue 2, Pg. 143-152

Document Type: Journal Paper


The speed characteristics of heavy vehicles on downgrades are analysed. The analyses were made by field observations of truck speeds on six rural two-lane downgrades. Loaded trucks considerably reduced their speeds at the beginning of a downgrade. The amount of reduction, termed the approach-speed gradient, was related to the length and slope of the downgrade, the second variable contributing exponentially to the increase in gradient. Buses and empty trucks increased their speeds at the downgrades studied. Using a previously developed model, which is based on delay measures and the speed distribution of trucks and passenger cars, passenger-car equivalents for downgrades are calculated and evaluated.

Subject Headings: Trucks | Vehicles | Passengers | Rural areas | Vehicle loads | Load factors | Slopes | Traffic delay

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