Rail Car Crashworthiness Design and Testing: Lessons Learned

Following National Transportation Safety Board (NTSB) recommendations and directions from early 1996, the Washington Metropolitan Transit Authority (WMATA) has worked to provide the latest crashworthiness and passenger safety requirements for its new car procurements. Taking advantage of recent developments in the field of vehicle crashworthiness, new technical requirements were developed and implemented for the 5000 and 6000 series vehicles. To date, WMATA is the first transit authority in the U.S. to require a dynamic sled test per the APTA SS-C&S-016-SS Standard, and the second (after the New York City Transit Authority) to run full-scale vehicle crash tests. Previously, the strength-based philosophy was used to ensure some level of rail vehicle crashworthiness. However, WMATA is now implementing a strength-based crashworthiness approach, augmented with “energy-based” requirements. Should a collision occur, the Authority’s ultimate goal is to reduce passenger deceleration rates during a collision, while at the same time controlling the absorption of collision energy in a manner that minimizes loss of space in the occupied volume of the vehicle. The passenger survivability measure using maximum acceleration has been supplemented by introducing the duration of the acceleration as an additional criteria following the Head Injury Criteria (HIC) and Abbreviated Injury Scale (AIS) approaches developed for the automotive industry. WMATA’s crashworthiness requirements now include sustaining a hard coupling without any damage to the body or coupler (except emergency release), and head-on collision of two eight-car trains with specified passenger loads (one train stationary with brakes applied) with no permanent deformation of the passenger compartment and with the acceleration, level and duration not to exceed the specified HIC. The implementation of an “energy-based” crashworthiness approach was divided into several logical steps/stages. During the design process, several modifications were introduced to optimize crashworthiness and to ensure structural compatibility with the existing fleet. The design was verified by implementing full-scale testing, and potential passenger injuries were assessed by using instrumented anthropomorphic test devices (ATDs), and measuring the forces and accelerations acting on these ATDs during the test.