Preliminary Evaluation of T-18's Gage Restraint Measurement System Tests [Research Results]
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Preliminary Evaluation of T-18's Gage Restraint Measurement System Tests [Research Results]

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      The Office of Research and Development of the Federal Railroad Administration (FRA), with the cooperation of the Union Pacific Railroad (UP), conducted a series of tests to determine if the new Gage Restraint Measurement System (GRMS) vehicle, T-18, can successfully test at 50 miles per hour (mph). The use of a deployable axle on the T-18 has virtually eliminated the risk of wide gage derailment by removing the split axle from the running truck, thus allowing the vehicle to test at higher speeds. Test speeds up to 35 mph are standard for GRMS vehicles owned by various railroads and private companies that provide service to the railway industry. Parameters that were important to successfully test at 50 mph were evaluated during the test along with the detection of any gage widening defects as described in the FRA Track Safety Standards.1 The ability of the load control system to maintain the preset loads within acceptable limits and the unloaded gage measurement system accuracy at higher speeds were the basic concerns. Detection of the same number of defects and the location of these defects at the two test speeds were the parameters used to evaluate GRMS ability to properly test track at higher speeds. Figure 1 shows the T-18 with the deployable split-axle in the test position. Results from the testing indicated that the vehicle could test at 50 mph while detecting track defects found at the standard test speed of 35 mph. The applied loads, especially the vertical load, had a higher standard deviation at the higher speed but were within the variation limit of the T-6 GRMS, the truck mounted split-axle. Although a higher variation existed on the loads, this should not preclude the testing at 50 mph since the new formulation for gage widening ratio (GWR)2 will take into account both the measured vertical and lateral loads. The accuracy of the mechanical unloaded gage measurement system is a concern, but since a laser unloaded gage measurement system is scheduled for installation on the T-18, this is not expected to prohibit to 50 mph testing. Further evaluation and data analysis are planned to obtain a better understanding of T-18’s capabilities and limitations at 50 mph operations.
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