Published in 2005
The intersection of a rail line and a roadway at an at-grade crossing represents the meeting of two vastly different transportation modes. Although they may share a common crossing where they intersect, the typical structural design of the supporting foundation for each is quite different. The design of a roadway consists of multiple layers of low-permeability materials, whereas the design of a rail line includes rails and crossties supported by open-draining aggregate ballast. Because of the use of highly permeable materials, the open draining nature of a rail line substructure can cause the early deterioration of a nearby roadway unless steps are taken to provide adequate drainage. In addition to structural differences, the rail line is designed to accommodate a substantial vertical deflection from passing loaded rail cars; it is common for a rail line to undergo up to 0.3 inch of vertical displacement. This large deflection can result in a greatly reduced service life for nearby pavements because of fatigue failure. Although it is inevitable that a rail crossing structure will have to undergo periodic reconstruction, selection of an optimum crossing surface constructed over an adequately prepared foundation will greatly increase the service life of the crossing. An optimum crossing structure can be viewed as one that combines safety, cost-effectiveness, long service life (reducing user costs by increasing the time between successive replacements), good performance, and ease of maintenance.
This report discusses the advantages and disadvantages of several crossing types that are the most appropriate for the conditions expected at the U.S. Route 29 and U.S. Route 15 crossings in Prince William County, Virginia. Specific recommendations for each crossing type are provided. It is the author’s opinion that the following crossing types represent the optimum alternatives for these locations and conditions in the following order: precast concrete platform panels, high rutresistant hot-mix asphalt; and steel-reinforced rubber panels. It is expected that these crossing alternatives will exceed the typical service life if the recommended materials and design elements are used.
Last updated: November 29, 2023