Liquefied Natural Gas Tender Crashworthiness in Train-to-Train Collisions

Research to facilitate industry efforts to safely use natural gas as a locomotive fuel is being directed by the Federal Railroad Administration’s (FRA’s) Office of Research, Development, and Technology. This research is being conducted cooperatively with the Association of American Railroads (AAR). The research results are being shared with the AAR’s Natural Gas Fuel Tender Technical Advisory Group (NGFT TAG), which includes AAR, Member Railroads, and FRA, with support from ARA and Volpe Center. The NGFT TAG is developing industry requirements, including crashworthiness requirements, for revenue-service natural gas fuel tenders. Five accident scenarios have been drafted by the NGFT TAG: a train-to-train collision, a grade-crossing collision, rollover, shell impact, and head impact. Each scenario includes a description of the equipment, the impact conditions, and the prescribed outcome. Conceptually, these tender scenarios parallel the scenarios described in 49 CFR Part 229 Appendix E for locomotive crashworthiness. The focus of the NGFT TAG discussions has expanded to include alternative static requirements. Conceptually, the tender static requirements parallel the requirements for locomotive crashworthiness in AAR S-580. Requirements in S-580 for locomotive structure include static load capacities, material properties, and material thicknesses. For conventionally-designed locomotives, meeting the static requirements of S-580 is accepted as meeting the dynamic requirements of Appendix E. The tender static requirements under development are intended to provide the same level of crashworthiness as the previously proposed dynamic requirements. The primary advantage of static crashworthiness requirements is that compliance can be shown with classical closed-form engineering analyses. A disadvantage is that design features are presumed, such as the inclusion and location of collision posts in a conventional locomotive design. Design features are not presumed in dynamic crashworthiness requirements; however, compliance must be shown with a design-specific validated computer simulation model. So while dynamic requirements allow for a wide range of design approaches, showing compliance often requires extensive effort. This paper focuses on technical information to help support development of alternative static requirements for the train-to-train collision scenario. The goal of the static requirements is to provide the same level of crashworthiness as the dynamic requirements under discussion by the NGFT TAG. Tender features capable of providing the desired level of performance are proposed. These features have been selected such that a tender with these features would be crashworthy-compatible with a wide range of new and existing locomotive structural designs.