Technology Digests / Longitudinal Rail Force Monitoring at FAST®

TD25-019

October 20, 2025
Authors
  • Stephen Wilk
  • Kenny Morrison
  • Christopher Johnson
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Key Findings

  • Between April 2024 and June 2025, the RNT at FAST generally remained within 10 degrees of the 100°F target RNT, but some regions of FAST experienced more RNT change than others.
  • FAST experiences RNT changes due to maintenance (rail breaks, welding, lining, etc.), longitudinal rail movement, and curve breathing. Many of these RNT changes are less than 10°F.
  • The largest RNT changes were attributed to maintenance, and these changes did not have a distinct pattern. Instead of decreasing, the RNT often increased, possibly due to some unique aspects of the measured FAST locations.
  • RNT changes from track movement are often associated with a visual indicator, such as loose anchors or disturbed ballast.

Longitudinal Rail Force Monitoring at FAST®

MxV Rail has been monitoring longitudinal rail forces (LRFs) and rail neutral temperature (RNT) at the Facility for Accelerated Service Testing (FAST®) since the completion of the FAST storage loop in April 2024.1 RNT is defined as the rail temperature at which the LRF is zero. The primary objectives of RNT monitoring at FAST are to ensure safe RNTs and to aid decision making, not necessarily to isolate or control variables. However, the RNT changes during normal FAST operations provide opportunities for MxV Rail engineers to 1) better understand the different causes of RNT changes, and 2) identify wayside and/or track-based measurements that can identify where RNT changes occur without prior knowledge. This effort is part of a larger initiative to shift away from blanket conservative assumptions (e.g., assume RNT loss of 30°F)2 and to better identify locations where RNT change has occurred using predictive models, measurement technologies, and indicators.…