Criteria and Procedures for Assessing Occupied Volume Integrity

With the potential for tremendous growth in the passenger rail industry, providing for the safety of the train-riding public and the crews who transport them becomes an ever-greater priority. To provide for safety while making best use of its resources and to facilitate passenger rail industry growth, the Federal Railroad Administration (FRA), in consultation with the rail industry, has developed alternative Criteria and Procedures for assessing the crashworthiness and occupant protection measures of rail passenger equipment. These Criteria and Procedures are intended to be applicable to a wide range of equipment designs, particularly equipment designs not complying with current U.S. standards and regulations. Because the latest technology in rail equipment crashworthiness has been used to develop the Criteria and Procedures, aspects of the resulting Criteria and Procedures are fundamentally different from their corresponding regulations. While technical results from sophisticated analyses and tests have been necessary, judgment was also needed to develop the Criteria and Procedures. This judgment was provided by the Engineering Task Force (ETF), and ultimately accepted by FRA. The ETF is a government/industry working group, organized under the auspices of the Railroad Safety Advisory Committee (RSAC). The Criteria and Procedures are intended to provide an engineering-based methodology for comparing the crashworthiness of alternatively-designed equipment with that of compliant designs. One particularly important aspect of passenger car crashworthiness is occupied volume integrity (OVI). It is essential that all passenger vehicles meet some base minimum level of OVI. A primary goal of crashworthiness is to maintain a volume for occupants to ride out a collision. In the U.S., this base level has been demonstrated through a vehicle’s ability to react a quasi-static load of 800,000 pounds along its line of draft without experiencing permanent deformation. This car-level requirement has existed, in some form, since the early 20^th century. However, alternatively-designed vehicles may not be able to demonstrate the ability to support this load, but may still prove to be equivalently crashworthy. Based on analyses performed on conventional and alternatively-designed passenger equipment, three options have been developed to demonstrate the OVI of alternatively-designed equipment. These options consist of three load magnitudes placed along the collision load path with a corresponding pass/fail criterion for each load. OVI may be demonstrated by sustaining an 800,000 pound load with no permanent deformation, a 1,000,000 pound load with limited permanent deformation, or a 1,200,000 pound load without exceeding the crippling load of the occupied volume. This paper discusses the pass/fail criteria associated with each option, the analysis and test procedures used in applying each option, and the technical basis used in developing the Criteria and Procedures for OVI evaluation. By applying such techniques, the results of evaluations of alternatively-designed equipment can be compared with the Criteria values for compliant designs. In this manner, the crashworthiness performance of alternatively-designed equipment can be assessed relative to the performance of compliant designs. A companion paper to this one discusses the development of the train-level Criteria and Procedures.