2022 Heavy Haul Session


Effects of Precision Scheduled Railroading (PSR) on derailment risk

Gary Wolf

Gary Wolf
Wolf Railway Consulting, LLC.

Precision Scheduled Railroading (PSR), and its many permutations and combinations, has been embraced by most railroads in North America. This presentation will address potential ramifications of these changes in operating practices on existing track maintenance policies. Specifically, changes in train tonnages, train lengths, train speeds and switching practices demand that track maintenance polices be reviewed and modified to ensure that the track structure is maintained to a high degree of reliability. Specific topics to be addressed include:

  1. Potential changes in train speeds (slower or faster) may require a complete review of curve elevation practices and spiral lengths to ensure wheel loads remain balanced on the high and low rail of curves. In addition, grinding practices should be reviewed to ensure rail profile shape is maintained for optimal steering in light of changing wheel forces.
  2. Longer and heavier trains will place increased tractive forces and thermal forces into the rails. This will require that rail anchoring, and ballast section, keep pace with these increased stresses.
  3. The use of more high adhesion AC locomotives will place higher longitudinal rail stress on a smaller footprint of the track structure, requiring improvements in rail anchoring to ensure longitudinal rail movement is minimized.
  4. Changes in traffic mix (less coal, more intermodal) could increase the risk of truck hunting, causing degradation of track gage on tangent tracks
  5. Changes in train blocking may increase the risk of greater slack action, placing larger lateral forces into track and elevating the risk of curve misalignment and panel shift.
  6. Longer and heavier trains may require a re-evaluation of track lubrication policies due to lower retentivity rates of both top of rail and gage face lubrication.
  7. The elimination of hump yards and shifting of switching to flat yards will require a review of moderately constructed track structure and turnouts in existing flat yards.
  8. Changes in track capacity may reduce the available windows for track maintenance and inspection.