Unlocked derailer
Pipeline and Hazardous Materials Safety Administration · Jun 18, 2008 · Reference No. 08-0127
Interprets: 49 CFR § 173.31
Reggie’s quick take
Someone asked whether an unlocked derailer meets § 173.31(g)(1), which requires access to track to be secured against entry by other rail equipment, including motorized service vehicles. In the scenario, the derailer sits between the railcar and a locked fence, unauthorized people cannot reach it, and only the shipper keeps its key. The agency says the requirement is met if the derailer can still perform its intended function in the unlocked position.
Written by AI (Claude) on Oct 22, 2026. Robots make mistakes and leave things out, so the letter below is what counts. Not legal advice.
This is in response to your April 28, 2008 letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180). Specifically you ask whether an unlocked derailer meets the requirements in § 173.31(g)(1) to secure access to track to prevent entry by other rail equipment including motorized service vehicles.
In your letter, you describe a scenario in which a derailer is positioned between the railcar and a locked fence. Both Ecolab Inc. and the railroad can unlock the fence to enable the exchange of rail cars. Unauthorized individuals are unable to access the derailer by the locked fence. Ecolab Inc. retains the only key to the derailer to prevent its unauthorized removal.
Provided the derailer can perform its intended function in the unlocked position, the requirement in § 173.31(g)(1) to secure access to the track to prevent entry by other rail equipment including motorized service vehicles is satisfied.
A letter of interpretation applies the regulations to the facts the requester described. It isn’t a regulation and isn’t legal advice. The agency’s copy.