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 hangup 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.

Current design vehicles do not address the hang-up problem. The hang-up problem depends on two factors, vehicle geometry and roadway geometry, and occurs at high-profile alignments. There is a need to establish design vehicle characteristics for hang-up prone vehicles to reduce the occurrence of hang-ups. Roadway geometry and vehicle characteristics relative to the hang-up problem were reviewed. Consideration of these properties by key organizations and associations, and government regulations were studied, and research performed by individuals establishing other design vehicles was analyzed. A general methodology was established: 1. Establish the Design Vehicles to be Developed 2. Determine the Dimensions / Characteristics to be Defined 3. Collect Appropriate Data 4. Use Data to Quantitatively Define Dimensions / Characteristics The design vehicles developed were chosen to represent the vehicle population. Variation in vehicle population, the ramifications of using a limited number of vehicles, and local conditions were considerations in selecting design vehicle types. Dimensions important to the hang-up problem (namely wheelbase, front/rear overhang, and ground clearance) were collected through field measurements and contacting manufacturers via telephone or Internet web pages. After establishing a database of measurements, the HANGUP software program was utilized to produce plots depicting hang-up points on four vertical curves and the spread of the database of dimensions for each design vehicle type with respect to those hang-up points. These plots displayed outliers in the database, allowing the researchers to select design vehicle dimensions that closely represented the vehicle population for each design vehicle type. The worst case dimensions (also plotted on the hang-up graphs) for wheelbase, front/rear overhang, and ground clearance were used as reference points for the establishment of design vehicle dimensions for all the vehicles save one, which utilized the 85 th percentile method to establish dimensions. Comparisons with AASHTO design vehicles were made. Constraints and considerations in establishing design vehicles were identified. Limitations found during the research included the geographic area and the infinite combinations of vehicles.