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Downhill Speed Control and the Use of Retarders on Heavy Trucks
Published January 01, 1983 by Institution of Mechanical Engineers in United Kingdom
Event: Braking of Road Vehicles
Countermeasures used in the United States to reduce the incidence of accidents involving runaway commercial vehicles are reviewed herein. A grade severity rating system is described in terms of (a) the manner in which the length, as well as the slope, of a grade influences its severity rating, (b) the tradeoff between vehicle weight and speed, and (c) the basis for the brake temperature calculations employed. The speed control available from retarders is examined in the context of a "truck retardation prediction procedure." This procedure calculates the influences of natural retardation engine drag, and retarder power on the equilibrium speeds attainable in various transmission gears for a vehicle of known weight operating on various levels of grade. The paper concludes with a discussion of the downhill speed control of retarder-equipped trucks.