Design vehicles were developed to evaluate the operation of low-ground-clearance, long-wheelbase, overhang vehicles on extreme hump or sag profile alignments. The literature review indicated that although formal studies had been conducted to develop design vehicles, these vehicles did not include the information needed to assess hang-up susceptibility on a particular vertical alignment. Relevant design vehicle dimensions for 17 vehicle types prone to hang-up were developed. Relevant dimensions included wheelbase, ground clearance, and front and rear overhang. These vehicles can be used in conjunction with the HANGUP software or other tools in designing vertical alignments that reduce the likelihood of hang-up problems. Because they are based on representative samples of both field-collected and manufacturers' data and have been evaluated using the HANGUP software, the design vehicles are reasonable and have a rational basis. The proposed vehicles should receive broad review with an eye toward inclusion in appropriate design policies and guidelines.
Abstract