Kristine Severson

Locomotive crashworthiness design modifications study

A study has been conducted of locomotive crashworthiness in a range of collision scenarios to support the efforts of the Locomotive Crashworthiness Working Group of the Federal Railroad Administrations Railroad Safety Advisory Committee (RSAC) to develop locomotive crashworthiness requirements. The RSAC is a government/industry committee including all segments of the rail community, with the purpose of developing solutions to safety regulatory issues. This paper presents the results of a study of the crashworthiness of conventional and modified locomotive designs in five collision scenarios.

Train-to-Train Impact Test: Analysis of Structural Measurements

This paper describes the results of the train-to-train impact test conducted at the Transportation Technology Center in Pueblo, Colorado on January 31, 2002. In this test, a cab car-led train, initially moving at 30 mph, collided with a standing locomotive-led train. The initially moving train included a cab car, three coach cars, and a trailing locomotive, while the initially standing train included a locomotive and two open-top hopper cars. The hopper cars were ballasted with earth such that the two trains weighed the same, approximately 635 kips each. The cars were instrumented with strain gauges, accelerometers, and string potentiometers, to measure the deformation of critical structural elements, the longitudinal, vertical, and lateral car body accelerations, and the displacements of the truck suspensions. The test included test dummies in the operator’s seat of the impacted locomotive, in forward-facing conventional commuter passenger seats in the cab car and first coach car, and in intercity passenger seats modified with lap and shoulder belts in the first coach car. During the train-to-train test, the cab car overrode the locomotive; the underframe of the cab car sustained approximately 22 feet of crush and the first three coupled connections sawtooth buckled. The short hood of the locomotive remained essentially intact, while there was approximately 12 inches of crush of the windshield center post. There was nearly no damage to the other equipment used in the test. The measured response of the trains compare closely with predictions made with simulation models.Copyright

CRASHWORTHINESS REQUIREMENTS FOR COMMUTER RAIL PASSENGER SEATS

Occupant experiments using instrumented crash test dummies seated in commuter rail seats have been conducted on board full-scale impact tests of rail cars. The tests have been conducted using both conventional cars and cars modified to incorporate crash energy management (CEM). Test results indicate that an improved commuter seat design could significantly reduce occupant injuries associated with collisions of CEM railcars. Commuter seats built to specific crashworthiness design requirements can mitigate the increased severity of secondary impacts associated with CEM equipment. In a collision, the leading car or two in a CEM consist may have a more severe longitudinal crash pulse than the leading car in a conventional consist. The crash pulse associated with a leading CEM cab car results in a higher secondary impact velocity between the unrestrained occupant and the seat, when compared to a conventional cab car. This conclusion applies to both rear- and forward-facing occupants. As a result, the seat must absorb more energy, which may cause significant deformation of the seat back, preventing occupant compartmentalization. Compartmentalization is an occupant protection strategy that aims to: contain occupants between rows of seats, provide a ‘friendly’ impact surface, and prevent tertiary impacts with other objects. To compartmentalize occupants during a collision, seats must be relatively stiff. To limit the forces and accelerations associated with occupant injury, the seat must be compliant, absorbing the occupant’s kinetic energy as it deforms. The objective of seat design crashworthiness requirements is to strike a balance between the competing objectives of compartmentalization and minimizing occupant injury. Work is currently on-going to design, build and test a prototype 3-passenger commuter rail seat that will improve interior crashworthiness. The first step is to develop the design requirements, which are based on a head-on collision between a CEM cab car-led train and a CEM locomotive-led train. The seat design will be evaluated using quasi-static and dynamic finite element analysis. The occupant response will be evaluated using a collision dynamics model two rows of seats and three Hybrid III 50 th percentile anthropomorphic test devices (ATDs). The seat design will be modified until the analytical models demonstrate that it meets the design requirements. Finally the prototype seat will be fabricated and tested quasi-statically and dynamically to ensure that the seat meets the design requirements. This paper describes the performance-based requirements that the prototype commuter rail seat must meet. Performancebased requirements include occupant compartmentalization, maximum allowable injury criteria, and maximum allowable permanent seat deformations. The paper also provides strategies for designing commuter seats that are better able to manage and dissipate the energy during a secondary impact. The paper describes computer models used to determine if the seats meet the design requirements.

Analysis of Collision Safety Associated With Conventional and Crash Energy Management Cars Mixed Within a Consist

A collision dynamics model of a passenger train-to-passenger train collision has been developed to simulate the potential safety hazards and benefits associated with mixing conventional and crash energy management (CEM) cars within a consist. This paper presents a comparison of estimated injuries and fatalities for seven collision scenarios based upon the variable mix of conventional and CEM cars. Based on the analysis results, recommended car placement when mixing cars within a consist is identified. The model includes a 6 car cab car-led consist colliding with a 6 car locomotive-led stationary consist. The stationary consist is made up of all conventional cars. The moving consist has a variable mix of conventional and CEM cars. For comparison, the bounding scenarios are: - a moving consist with all conventional cars, and - a moving consist with all CEM cars. The collision speed ranges from 15 to 35 mph. Since the two car designs behave differently under impact conditions, there is a concern that there may be hazards associated with mixing the two designs in the same consist. In none of the cases evaluated is the mixed consist less crashworthy than the conventional consist. The modeling results indicate that the least crashworthy consists are ones in which a conventional cab car is leading any combination of vehicles. The conventional cab car incurs nearly all the damage and prevents trailing cars from participating in energy absorption, whether they are conventional or CEM. The most crashworthy consists are ones in which a CEM cab is leading. The CEM cab can absorb a significant amount of energy without intruding into the occupied volume. The CEM cab also allows trailing cars to participate in energy absorption, which provides further occupant protection. The recommended strategy for car placement is to put the CEM car(s) at the leading end(s) and the conventional car(s) at the trailing end or in the middle of the consist in push-pull operation. There is also significant benefit to placing the seats in the leading CEM car or two so they are rear-facing. Rear-facing seats can reduce the severity of secondary impact injuries because the occupant is already in contact with the seat in the direction of travel and does not develop a significant velocity relative to the seat.© 2003 ASME

Two-car impact test of crash energy management passenger rail cars : analysis of occupant protection measurements

As a part of ongoing passenger rail equipment safety research, a full-scale impact test of two cars with energy absorbing end structures was carried out on February 26, 2004. In this test, two coupled cars impacted a rigid barrier at 29 mph. Similar to previous full-scale tests in the series [1,2,3], anthropomorphic test devices (or ATDs) were included on the rail cars to measure the occupant response during the collision. These ATDs were instrumented with accelerometers and load cells to measure the injury risk to the occupants. This paper presents preliminary tests results. Five occupant experiments were included in the two-car test. Three of the experiments were similar to those conducted on the two-car test of conventional equipment that was held on April 4, 2000: forward-facing occupants in inter-city seats, forward-facing occupants in commuter seats, and rear-facing occupants in commuter seats. Two of the experiments examine the interaction of an occupant with a workstation table in a facing-seat configuration. These two tests used experimental ATDs with an increased capacity for recording abdominal impact response. To aid the analysis of this problem, MADYMO computer models were developed for four of the five of the occupant experiments. The models were either modified from earlier simulations, in the case of the commuter seats, or newly developed, in the case of the inter-city seats and table experiment with THOR ATD. The models were validated based on previous tests and/or accident data. Predictions of the ATD response agree closely for the overall kinematics of the ATDs, and for many of the measurements made with the ATDs in the full-scale test.Copyright

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

DEVELOPMENT OF PERFORMANCE REQUIREMENTS FOR A RAIL PASSENGER WORKSTATION TABLE SAFETY STANDARD

The American Public Transportation Association’s (APTA) Construction and Structural committee, a railroad industry group, with the support of the Federal Railroad Administration (FRA) and the John A. Volpe National Transportation Systems Center (Volpe Center), is creating an industry safety standard for an energy absorbing table. Workstation tables in passenger trains are an increasingly popular seating configuration both in the United States and abroad. Although a well-attached table can provide convenience and compartmentalization for the occupant, there is a risk of abdominal injury during a rail accident. In Fact, there have been several accidents in the United States in which impacts with workstation tables have severely or fatally injured occupants. In 2006, in response to these injuries, an FRA sponsored program developed a prototype table that distributed load over a wider area of the abdomen and absorbed energy during a collision. This table design was tested with specialized anthropomorphic test devices (ATDs) instrumented to measure abdominal impact response and was shown to decrease injury risk compared to a baseline table design. Building on the knowledge gained in the development of the prototype table, the proposed standard requires force to the abdomen be limited while energy is absorbed by the table. Since manufacturers do not have access specialized ATDs, researchers proposed a two part testing requirement. The first part is a quasi-static test which measures the energy absorption capacity of the table with a maximum force level determined from testing with specialized abdominal ATDs. The second part is a sled test with a standard Hybrid III 50th percentile (HIII) ATD to assess compliance with occupant protection standards of compartmentalization and ATD injury assessment reference values (IARVs). This paper discusses the research performed to develop the performance requirement in the draft standard. Current injury measures, originally developed for the automotive industry, were examined to assess their applicability to workstation table impacts. Multiple Mathematical Dynamic Models (MADYMO) model simulations show the estimated injuries during a simulated sled test scenario. Several force-crush parameters were examined, including the initial stiffness of the force-crush curve, the plateau force and the target energy absorbed by the table, to determined the force-crush design characteristics of a table that are likely to reduce injury risk. The results of this study, combined with testing of the current prototype table described in a companion paper [1], led to a draft standard that will greatly improve the safety of workstation tables in passenger rail cars.

Research into Integrity of Glazing for Passenger Rail Equipment

This research into the integrity of glazing is spurred by recent accidents, including the commuter train derailment in Spuyten Duyvil, New York, on December 1, 2013. Four passengers were fatally injured in that accident. All four fatalities were attributed to ejection through window openings. Results of the accident investigation indicate that the rubber gaskets holding the window panes in place pulled out when the cars slid on their sides after leaving the track. The windows were pushed inside the cars and created openings that allowed occupants to be ejected. After its investigation, the National Transportation Safety Board issued a recommendation for more-effective passenger containment by glazing systems in derailments. In addition to functioning as windows, glazing systems are also expected to be impact resistant, to provide emergency egress and emergency access, to be fire resistant, and to provide occupant containment. Research activities include assessing the performance of current glazing systems in meeting all expectations, especially occupant containment, developing modifications for improving safety performance, and comparing the performance of conventional and modified glazing systems. The objective of the Federal Railroad Administration’s (FRA’s) research into the integrity of glazing is to describe comprehensively all the engineering requirements placed on glazing systems and to develop effective strategies for balancing all the safety demands. The integrity of glazing is one of many research topics on the crashworthiness of rail equipment and is conducted by FRA in coordination with other topics, such as the integrity of the side structures of passenger equipment and the protection of occupants.