Volpe Center: Volpe Center Highlights

Information Resources

Volpe Center Highlights - January/February 2004

Focus

Progression photos of tests of conventional rail passenger equipment (bottom) to cars retrofitted with designs intended to improve crashworthiness (top).

The Volpe Center has designed a series of tests to measure and compare the crashworthiness performance of conventional rail passenger equipment (bottom) to cars retrofitted with designs intended to improve crashworthiness (top).

Promoting and Improving the Safety of Rail Service

The resurgence of intercity and commuter passenger rail service in the United States offers travelers viable options to air and highway travel, which can translate into reduced traffic congestion and fewer environmental impacts. In response to increased demand for service, new equipment is being developed. However, as rail traffic and speed increases, so does the potential for accidents, serious injuries, and fatalities; until recently there were no federal or industry standards governing the safety performance of new equipment designs. Ongoing Volpe Center research in support of the Federal Railroad Administration (FRA) is contributing to new regulations and standards that will help protect passengers and crew members in the event of rail accidents.

In collaboration with the FRA's Equipment Safety Research Program, the Volpe Center has supported a testing program that determines the performance of both conventional and improved crashworthiness designs of passenger rail cars. Volpe's principal role has been to conduct the research, which involves defining appropriate scenarios to study collisions, developing computer models to simulate the structural and dynamic results of the collisions, designing and supervising the full-scale tests, processing the test data, and comparing the test measurements with the analysis results. The computer models are then used to evaluate a wider range of collision conditions than can be tested.

The test vehicle was a Budd Pioneer cab car retrofitted with an end structure of crash energy management design.

Performing Full-Scale Rail Car Testing
The first series of full-scale tests defined the crashworthiness of conventional-design equipment in three impact conditions. Corresponding tests of modified passenger rail cars have begun. This testing arrangement allows comparison of the performance of both types of equipment. The Volpe team determines what studies and tests need to be performed, defines objectives, carries out the studies and tests (both inhouse and with contractor support), and applies the results to develop recommendations for rail equipment crashworthiness standards and regulations.

Computer illustration of finite element model.

The specific crash energy management design selected for the rail car test is a series of trigger mechanisms and crushable components that, when activated, cause the end of the car to crush in a controlled manner. There are three primary crushable elements: the pushback coupler module, the primary energy absorbers, and the roof absorbers.

On December 3, 2003, a single-car impact test was conducted to assess the crashworthiness performance of a passenger rail car retrofitted with crash energy management (CEM) crush zones. The CEM design is intended to limit the structural damage from intruding into the passenger compartment. Mr. David Tyrell, Mr. Eloy Martinez, and Ms. Karina Jacobsen of the Structures and Dynamics Division traveled to the Transportation Technology Center, an intermodal research and test center in Pueblo, Colorado, to supervise the implementation of the test. In test conditions similar to those of the earlier corresponding conventional-car test, the retrofitted CEM car was pushed up to nominally 35 mph and collided with a rigid barrier. The vehicle was instrumented to capture several categories of data; high-speed film and video provided a secondary set of data.

The preliminary test results indicate that the CEM design has superior crashworthiness performance over conventional equipment. The conventional car experienced more than 5 feet of crush, whereas the CEM design was about 3 feet, limiting the vehicle damage to the unoccupied volume.

Computer models, such as those shown below, are used to simulate the full-scale impact tests. Finite element models provide information on the structural force/crush behavior. A collision dynamics model then uses the force/crush characteristic to produce estimates of the gross motions of the colliding bodies.

Finite element model

Collision dynamics model

CEM is engineered by using zones of controlled crush; the collision energy is absorbed by a series of components with known structural characteristics. The crush is distributed throughout the length of a train, limiting damage to unoccupied areas in multiple cars rather than crushing large volumes of the first car, as is characteristic of existing equipment. The test results show that the CEM crush zone performed as engineered. In comparison with pre-test design estimates, the overall test performance was in close agreement.

Single-car test data is currently being further processed and analyzed. Additionally, test results are being used to refine the test model. Upcoming tests of the CEM design include a two-coupled car impact with a fixed barrier, which will include interior-occupant tests, and a cab car-led train impacting a locomotive-led train.

Validating and Improving Computer Models
While the principal objective of this testing program is to determine effective strategies for improved structural crashworthiness and improved occupant protection, a secondary objective is to validate and improve the computer models that have been developed as part of rail vehicle crashworthiness research. As part of test planning, detailed computer simulations are performed prior to each test.

The results of the simulations are used to determine the impact speed as well as other details of the test, such as accelerometer size and location. After the test, the simulation results are compared with the test measurement and the analyses are refined as necessary.

Impacting Federal Regulations and Industry Standards
Results of this research have been used to develop the crashworthiness requirements for Amtrak's high-speed trainset, to develop and improve the FRA's Passenger Equipment Safety Standards, and to draft revisions and additions to FRA locomotive crashworthiness regulations as well as the Association of American Railroads (AAR) standards. The American Public Transportation Association (APTA) is using information from this research to further develop and refine industry standards and recommended practices for rail passenger equipment crashworthiness.

Through APTA and AAR, the railroads and suppliers are involved in planning and conducting crashworthiness studies. The results are presented to these organizations, and are documented in government reports and in technical papers written for the American Society of Mechanical Engineers, the Transportation Research Board, and other technical organizations.

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