United States Department of Transportation
i
New Methods for Determining Requirements for Truck-Climbing Lanes
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1989-09-01
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[PDF-457.46 KB]
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Abstract:To facilitate traffic flow and to improve highway safety on upgrades, highway design engineers have constructed hill-climbing lanes. A recent FHWA-sponsored study found that current guidelines may be leading designers to overdesign highways, adding and maintaining unnecessary hill-climbing lanes. The report summarized here highlights four major findings of the earlier FHWA study: (1) current design guidelines are conservative for single-unit trucks and tractor-semitrailers and current critical lengths of grade are thus shorter than these two truck types would warrant, (2) single-unit trucks with trailers and doubles do not perform nearly as well as single-unit trucks and tractor-semitrailers, which may indicate that the performance of the latter two types of trucks match current guidelines, (3) critical length of grade should be based on the weight-to-available power ratio of current truck mix, rather than on assumptions about the performance of a 300-lb/hp truck which was typical in 1965, and (4) highway designers need more comprehensive methods for deciding when hill-climbing lanes are warranted. This report also presents tools developed in the study for designing hill-climbing lanes. This report was based on the following study: "Methods for Predicting Truck Speed Loss on Grades - Final Technical Report: FHWA/RD-86-059" (A).
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