TRACK STRUCTURE SYSTEMS

The railway track-system concept is a way of looking at things that takes into account secondary and tertiary effects in the totality of cause and effect. A track system is not simply a collection of curves, tangents, switches, frogs, turnouts, crossings, and crossovers, but includes the interrelations among the various components--the rails, ties, ballast, fasteners, and subgrade. One of the earliest railway engineers to employ system thinking was Robert L. Stevens of New Jersey, who in 1830 conceived the flat-bottomed-tee rail and the first cut spikes and joint bars. Later, he evolved the idea of wooden crossties. He single-handedly developed the basic system of mutually complimentary components used in railroad trackage today. The next system thinker to have a profound influence on track technology in North America was Arthur N. Talbot of the University of Illinois, who developed the concept of the modulus of elastic track support, first reported in 1918. This was a quantifiable response to load of ties, ballast, fasteners, and subgrade material that can be used to predict track deformation under vertical load. The Stevens' legacy was a system design of railway track, and Talbot's contribution was a system analysis of track structure. Talbot also left a challenge because, while track performance can be predicted when the modulus is known, how to design to a modulus has not yet been learned. The rate of return on incremental investment in individual track components can be determined only by full-scale experiments. The new full-scale laboratory the Association of American Railroads is building in Chicago should bring about validation of mathematical models of track that are being developed. This new laboratory will permit applications of calibrated loads to full-scale test sections of track, and the resulting deformations and stresses can be measured. The really important system is not the track system nor the equipment system, but the train-and-track system. An example of train-and-track system thinking occurred in 1934 when the Pennsylvania Railroad chose the GG-1 locomotive over its competitor because of lower wheel and axle loadings. Technical decisions must be influenced by economic and political factors, and track systems are no exception. An example today is the question of proper superelevation on curves, and the answer depends in part on the kind and amount of intercity rail passenger service that will be provided, which is a political question. Even more significant is the question of right-of-way ownership. Would a private company choose a lower axle-load locomotive if it were to be operated over track the company did not own?

Media Info

  • Media Type: Print
  • Pagination: pp 21-24
  • Monograph Title: Track systems and other related railroad topics
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00183888
  • Record Type: Publication
  • ISBN: 0309026822
  • Files: TRIS, TRB
  • Created Date: Dec 3 1978 12:00AM