Amtrak Petitions FRA for Waiver of Compliance Regarding Loss of Shunt Incidents

Written by Carolina Worrell, Senior Editor
(FRA image)

(FRA image)

Amtrak on Oct. 17, 2023, petitioned the Federal Railroad Administration (FRA) for a waiver of compliance from certain provisions of the Federal railroad safety regulations contained at 49 CFR part 229 (Railroad Locomotive Standards).

According to FRA, Amtrak’s petition seeks approval to install, on its locomotive fleet, equipment designed to improve shunting of railroad track circuits and reduce the potential for a loss of shunt (LoS) incident (a shunt enhancer antenna).

LoS within a track circuit causes a signal system or grade crossing system to not detect the presence of a train, significantly increasing the risk of train-to-train collisions and crossing accidents. According to FRA, known causes of LoS include contaminants on the wheel or rail and locomotive weight, with contributing factors including the number of axles in a train, train speed, wheel profile, and weather. FRA says it recognizes that a LoS event is “a significant safety concern, resulting in both activation failures at equipped highway-rail grade crossings and false proceed signals.”

Over the last five years, an industry-led working group, the LoS Committee, supported by FRA, has expended significant effort and funding to investigate LoS events, evaluate LoS causes, identify potential solutions, and to test those solutions. The shunt enhancer antenna, FRA says, has been “identified, tested, and recommended” by the LoS Committee, which has confirmed that the shunt enhancer antenna “reliably demonstrate[s] improvement of a vehicle’s interaction with the wayside track circuits.”

Amtrak seeks relief from 49 CFR 229.71, Clearance above top of rail, to implement the locomotive-mounted shunt enhancer antenna. Section 229.71 states that no part or appliance of a locomotive (excepting “the wheels, flexible nonmetallic sand pipe extension tips, and trip cock arms”) may be within 2.5 inches from the top of rail. Amtrak, which seeks to install the shunt enhancers on its fleet of Siemens Charger SF4 locomotives, explains that under conditions of worn wheels and dynamic profiles, “the mechanical and electrical hardware of the truck-mounted antenna devices could protrude below 2.5 inches from the top of rail.”

FRA says it understands the proposed shunt enhancer antenna is a truck-mounted antenna that injects a 2-4 amp, 165kHz signal into the rail.

Interested parties are invited to participate in these proceedings by submitting written views, data, or comments. FRA says it does not anticipate scheduling a public hearing in connection with these proceedings since the facts do not appear to warrant a hearing. If any interested parties desire an opportunity for oral comment and a public hearing, they should notify FRA, in writing, before the end of the comment period and specify the basis for their request.

Communications received by June 18, 2024, will be considered by FRA before final action is taken. Comments received after that date will be considered if practicable.

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