Analysis and design procedure for highway-railroad grade crossings

Abstract

Both highway and railroad organizations are concerned with the maintenance problems of highway-railroad grade crossings. The Texas State Department of Highways and Public Transportation alone spends approximately one-half million dollars yearly for the maintenance of its grade crossings. It has been the usual experience of engineers and it is a conviction implicit in this study that a major portion of such maintenance costs may be reduced by an improved knowledge of actual behavior of a railroad track under both railway and highway traffic and the influence of environmental factors. Up to the present time, no rational approach to analysis and design of a grade crossing structure has been available. In this study a design system for a grade crossing is developed. A unique design criterion of permanent differential deformation between railroad track and adjacent highway pavements is established. This criterion is related to other existing criteria, available in pavement design literature, which are related to the rideability. Polynomial stress equations are developed separately for railroad and highway pavements under their typical design wheel loads to predict stresses at different depths. Characteristic properties of all materials involved, such as resilient modulus and permanent deformation under repeated loading are considered. The influence of environmental factors such as temperature and moisture balance on subgrade material characteristics is also included. A computer program is developed to calculate the differential deformation (the design criterion) for the purpose of the design of a grade crossing. The concept of differential deformation as a design criterion and the design system proposed in this dissertation constitutes a new and rational approach to the design of highway and railroad grade crossings. Several example problems are presented to illustrate the whole design system. These examples also illustrate how these designs must change according to the variations in expected loading, temperature, climatic zone, and subgrade soil.