Track Substructure Design Methodology and Data

Track substructure design is an often overlooked step in the design of railroad track. The lack of consideration for the substructure when designing track results in greater maintenance demands due to inadequate track substructure performance. Railway track is a stable structure with a progressive failure process that allows track engineers to manage the degradation of the track through maintenance. However, increasing demands for track availability from high traffic volumes require that track maintenance be minimized while ensuring safety. Additionally, developing high speed rail and intercity passenger rail on existing corridors necessitates higher levels of substructure performance due to tighter track roughness tolerances. Reduction in maintenance needs can be achieved by ensuring that new construction and rehabilitation projects be designed to provide a stable track structure throughout the design life. Lack of readily available data for substructure materials is a drawback to the use of track design methods. This paper provides a summary of several available substructure track design methods along with the required data for design. The track design data is related to track measurements that could be used to determine much of the information necessary for design of track rehabilitation. Track load-deflection data could be used to develop much of the needed design data while ground penetrating radar could support delineation of similar track segments. Benefits of track structure design include knowledge of expected life, reduced maintenance, material properties for quality control, and development of material properties that could permit application of performance based contract specifications.