Effectiveness of alternative rail passenger equipment crashworthiness strategies

Crashworthiness strategies, which include crash energy management (CEM), pushback couplers, and push/pull operation, are evaluated and compared under specific collision conditions. Comparisons of three strategies are evaluated in this paper: push versus pull operation (cab car led versus locomotive led consists); conventional versus CEM consists; and incremental CEM versus full-CEM. Rail cars that incorporate CEM are designed to absorb collision energy through crushing of unoccupied structures within the car. Pushback couplers are designed to recede into the draft sill under collision loads and enable the car ends to come into contact, minimizing the likelihood of lateral buckling. Push/pull operation refers to operating either a locomotive (pull mode) or a cab car (push mode) at the leading end of the train. Five cases using combinations of these three strategies are evaluated. The basic collision scenario for each case analyzed in this paper is a train-to-train collision between like trains. Each train has a locomotive, four coach cars, and a cab car. The impact velocity ranges from 10 to 40 mph. The following five cases are evaluated: (1) all conventional cars with a cab car leading (baseline case); (2) all conventional cars with a locomotive leading; (3) conventional coach cars with pushback couplers, with CEM cab car leading; (4) all CEM cars with a cab car leading: (5) all CEM cars with a locomotive leading. A one-dimensional lumped-mass collision dynamics model is used to evaluate the effectiveness of each strategy, or combination of strategies, in terms of preserving survivable space for occupants and minimizing secondary impact velocity (SIV). Test data is used to correlate SIV with head, chest, and neck injury. Probability of serious injuries and fatalities are calculated based on calculated car crush and injury values. The maximum crashworthy speed, or the maximum impact speed at which everyone is expected to survive, is calculated for each case. Of the five cases evaluated, the scenario of a cab car led conventional consist represents the baseline level of crashworthiness. The highest levels of crashworthiness are achieved by a consist of all CEM cars with a locomotive leading, followed by all CEM cars with a cab car leading. The results indicate that incremental improvements in collision safety can be made by judiciously applying different combinations of these crashworthiness strategies. A CEM cab car leading conventional cars that are modified with pushback couplers enhances the level of crashworthiness over a conventional cab car led consist and provides a level of crashworthiness equal to a locomotive leading conventional passenger cars