FRA: ‘High-Impact Wheels Causing Damage to Rails, Track Structures’

Written by Marybeth Luczak, Executive Editor
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The Federal Railroad Administration (FRA) on Sept. 7 issued Safety Advisory 2023-04 recommending that railroads use Wheel Impact Load Detectors (WILD) “to properly identify and replace high-impact railcar wheels that could cause significant damage to rails and supporting track structures.”

The advisory (download below) follows FRA’s preliminary investigation of a February 2023 Union Pacific coal train derailment in Gothenburg, Neb., which the agency said indicates that “high-impact wheels damaged the rail the train was operating over and caused the derailment.” Current industry practices for using WILDs, FRA reported, “could help prevent such incidents in the future.”

FRA investigation records show that one of the 30 freight cars that derailed had a WILD measurement of 130.6 KIPs when it operated over the track joint bar that was found broken, the agency reported. “Records also show this freight car continued to operate for several months prior to the derailment after its high-impact wheels were identified by WILDs,” according to FRA. “WILD measurements showed high-impact wheels in November and December 2022, and again in January 2023. During its investigation, FRA also identified eight other freight cars in the derailed train with high-impact wheels.”

FRA reported that it is recommending that railroads and contractors “continue to use WILDs to help identify and replace high-impact wheels according to railroad current industry practices.” Specifically, it said, “wheels with a WILD measurement greater than 80 KIPs should be replaced when in a repair shop, and wheels with a WILD measurement greater than 90 KIPs should be replaced when found in any other location in service.” Also, railroads “should review procedures for identifying dynamic ratios to help predict high-impact wheels when cars are loaded,” according to FRA. The agency defined dynamic ratio as “the ratio of a WILD measurement of a loaded railcar compared to when it is empty.” The peak impact, it said, is the “highest WILD measurement recorded.” The impact measurement, it noted, varies during operation “due to the changing operating environment, including changes in speed.” Wheels should be replaced “when an empty railcar with a dynamic ratio of five or higher has a preceding peak impact greater than 100 KIPs,” which FRA said, “will reduce or eliminate further damage to the freight car’s wheels, rails and track structures.”

FRA also recommended that railroads and contractors review Safety Advisory 2023-04, “High-Impact Wheels Causing Damage to Rails and Track Structures,” with employees “to increase their awareness of the possible consequences of allowing freight cars with high-impact wheels to continue to operate.”


According to FRA, in 2015 it issued Safety Advisory 2015-01, recommending, among other things, the use of WILDs “to improve safety, recognizing the potential value of these wayside detection systems, if they are appropriately installed, maintained and utilized,” according to the agency. It also recommended that railroads “continue to install and maintain WILDs along certain routes and monitor their measurements to determine when to replace wheels.” Additionally, in that Safety Advisory, FRA suggested that railroads “lower the impact threshold for action to replace the wheels on any car in a high-hazard flammable train.”

According to FRA, WILDs “supplement, and do not substitute, the existing wheel regulations that focus on preventing broken wheels and other wheel failures.” WILD measurements “are intended to focus more on the interaction between the wheels and the rail and prevent broken rails and other rail failures,” it said. WILDs are designed “to measure the impact of a railcar’s wheels on the rail and alert the operating railroad and car owner when wheels have a high impact,” it explained. “WILDs measure this impact on the rail in KIPs (1,000 pounds-force). High-impact wheels (generally considered to be more than 90 KIPs) are typically caused by a flat spot or other wheel defect. If not addressed, high-impact wheels can damage rail and track structures and cause a derailment.”

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