Overview of a crash energy management specification for passenger rail equipment

At the request of METROLINK, the Federal Railroad Administration (FRA), with the Federal Transit Administration and the American Public Transportation Association, formed the ad hoc Crash Energy Management Working Group in May 2005. This group developed recommendations for crush zones in passenger rail cars for METROLINK to include in its procurement specification. The Volpe Center provided the Working Group with technical information from the research on passenger rail equipment crashworthiness it is conducting for FRA. METROLINK released its specification, including the recommendations from the Working Group, on September 16, 2005, as part of an invitation forbid. The specification includes three levels of requirements: train, car, and mechanism. The train level requirements specify a collision scenario for which there must be no intrusion into the occupied areas and limits on the relative velocities at which the operator and passenger may impact interior surfaces. The car and mechanism level requirements follow from the train level requirements. The car level requirements include specifications for a cab end crush zone capable of absorbing 3.0 million ft-lbs of energy and a non-cab end crush zone capable of absorbing 2.0 million ft-lbs. There are also specifications on the crush zone kinematics and on the target force/crush characteristics. Mechanism level requirements include specifications for the coupling mechanism, the load transfer mechanism, and the principal energy absorption mechanism. The coupling mechanism permits the coupler to push back, allowing the ends of adjacent cars to remain aligned and come together during an impact. The load transfer mechanism transmits the load from the adjacent equipment into the crush zone in a manner that allows the principal energy absorption mechanism to function as intended. The cab end load transfer mechanism can include a deformable LD that acts similarly to an automobile bumper, and resolves eccentric impact loads into loads that can be appropriately reacted by the supporting structure. The principal energy absorption mechanism is the section of the carbody structure intended to deform gracefully and to provide most of the required energy absorption. The specification prescribes performance for the train, the cab and trailer cars, and the mechanisms. Each requirement includes quantitative criteria for evaluation of compliance. The Working Group extensively discussed various evaluation methodologies, including non-linear large deformation finite element analysis and dynamic component tests, and worked to assure that practical evaluation methodologies are available for each requirement. For components critical to the functioning of the crush zone, tests are required. This paper describes the requirements, the associated criteria, and the available evaluation techniques. The technical bases driving the need for each of the requirements are discussed.