Author: Ronald W. Eck, S.K. Kang

Date of Publication:  1991

Sponsoring Agency:  Mid-Atlantic Universities Transportation Center, The Pennsylvania State University and Division of Highways, West Virginia Department of Transportation

Performing Agency:  Department of Civil Engineering, West Virginia University

Abstract:

When a long wheelbase and/or low ground-clearance vehicle negotiates a high profile roadway, such as a railroad-highway grade crossing, the vehicle may become lodged or stuck on the “hump” and subsequently be struck by a train. Types of low ground-clearance vehicles include low-boy equipment trailers, car carriers, double drop van trailers, and cars/trucks with trailers.

A literature review revealed there are no general highway design standards aimed at providing adequate ground-clearance on highways. Similarly, there was a lack of data relative to the magnitude of the low-clearance vehicle incident problem and on low-clearance vehicle characteristics.

Low-clearance vehicles, including heavy trucks plus light trucks and automobiles with trailer combinations, comprised 2.0 percent of the traffic stream. Based on the field data, a design low-clearance vehicle was proposed whose dimensions are a 36-ft wheelbase and S-inch ground-clearance. These represent the 85th percentile of the low-clearance vehicle dimensions collected.

Microcomputer software was developed to simulate the movement of trucks over high profile roadways so that any highway engineer can analyze low-clearance problems. Using the software package and the field data on low-clearance vehicles, specific design criteria were developed for highway vertical alignment at railroad-highway grade crossings. Design standards to accommodate low-clearance vehicles on vertical alignment in general were also formulated. The standards provide (in the form of tables and figures) recommended profiles for cross-sections at intersections and vertical alignment of driveways.
 

No. of Pages:  197