Research to develop new technologies for increasing the safety of passengers and crew in rail equipment is being directed by the Federal Railroad Administration’s (FRA’s) Office of Research, Development, and Technology. Crash energy management (CEM) components which can be integrated into the end structure of a locomotive have been developed: a push-back coupler and a deformable anti-climber. These components are designed to inhibit override in the event of a collision. The results of vehicle-to-vehicle override, where the strong underframe of one vehicle, typically a locomotive, impacts the weaker superstructure of the other vehicle, can be devastating. These components are designed to improve crashworthiness for equipped locomotives in a wide range of potential collisions, including collisions with conventional locomotives, conventional cab cars, and freight equipment. Concerns have been raised in discussions with industry that push-back couplers may trigger prematurely, and may require replacement due to unintentional activation as a result of loads experienced during service and coupling. Push-back couplers (PBCs) are designed with trigger loads meant to exceed the expected maximum service and coupling loads experienced by conventional couplers. Analytical models are typically used to determine these trigger loads. Two sets of coupling tests have been conducted that validate these models, one with a conventional locomotive equipped with conventional draft gear and coupler, and another with a conventional locomotive retrofit with a PBC. These tests allow a performance comparison of a conventional locomotive with a CEM-equipped locomotive during coupling, as well as confirmation that the PBC does not trigger at speeds below typical coupling speeds. In addition to the two sets of coupling tests, car-to-car compatibility tests of CEM-equipped locomotives, as well as a train-to-train test are also planned. This arrangement of tests allows for evaluation of the CEM-equipped locomotive performance, as well as comparison of measured with simulated locomotive performance in the car-to-car and train-to-train tests. The conventional coupling tests and the CEM coupling tests have been conducted, the results of which compared favorably with their pre-test predictions. In the CEM coupling tests, the PBC triggered at a speed well above typical coupling speeds. This paper provides a comparison of the conventional coupling test results with the CEM coupling test results. The next test in the research program is a vehicle-to-vehicle impact test. This paper describes the test preparation, test requirements, and analysis predictions for the vehicle-to-vehicle test. The equipment to be tested, track conditions, test procedures, and measurements to be made are described. A model for predicting the behavior of the impacting vehicles and the CEM system has been developed, along with preliminary predictions for the vehicle-to-vehicle test.

Over the past several years, Carbuilders have been developing car designs that utilize Crash Energy Management (CEM) as an alternative means to demonstrate compliance with carbody structural strength requirements. With the onset of CEM designs, the CFR has been amended to include requirements for alternative compliance to carbody structure requirements (see Docket No. FRA-2013-0060, Notice No. 3, [the Final Rule]) [14]. CEM designs often utilize crush zones with the overall goal of protecting occupant volume. These designs also change the structural behavior of the car during an accident, resulting in different acceleration responses than conventional car designs. This paper seeks to compare and contrast the interior fitting strength requirements between conventional car designs and a generic CEM design. The methodology utilizes simple mathematical simulations, modeling a conventional car design and a CEM design, with outputs of the simulation consisting of car response and behavior. Results indicate that alternative compliance requirements for all tiers of CEM-designed passenger equipment should be considered for interior fixtures.

Research to develop new technologies for increasing the safety of passengers and crew in rail equipment is being directed by the Federal Railroad Administration’s (FRA’s) Office of Research, Development, and Technology. Crash energy management (CEM) components which can be integrated into the end structure of a locomotive have been developed: a push-back coupler and a deformable anti-climber. These components are designed to inhibit override in the event of a collision. The results of vehicle-to-vehicle override, where the strong underframe of one vehicle, typically a locomotive, impacts the weaker superstructure of the other vehicle, can be devastating. These components are designed to improve crashworthiness for equipped locomotives in a wide range of potential collisions, including collisions with conventional locomotives, conventional cab cars, and freight equipment. Concerns have been raised in discussions with industry that push-back couplers may trigger prematurely, and may require replacement due to unintentional activation as a result of service loads. Push-back couplers (PBCs) are designed with trigger loads meant to exceed the expected maximum service loads experienced by conventional couplers. Analytical models are typically used to determine these required trigger loads. Two sets of coupling tests have been conducted to demonstrate this, one with a conventional locomotive equipped with conventional draft gear and coupler, and another with a conventional locomotive retrofit with a push-back coupler. These tests will allow a performance comparison of a conventional locomotive with a CEM-equipped locomotive during coupling. In addition to the two sets of coupling tests, car-to-car compatibility tests of CEM-equipped locomotives, as well as a train-to-train test are also planned. This arrangement of tests allows for evaluation of the CEM-equipped locomotive performance, as well as comparison of measured with simulated locomotive performance in the car-to-car and train-to-train tests. The coupling tests of a conventional locomotive have been conducted, the results of which compared favorably with pre-test predictions. This paper describes the results of the CEM-equipped locomotive coupling tests. In this set of tests, a moving CEM locomotive was coupled to a standing cab car. The primary objective was to demonstrate the robustness of the PBC design and determine the impact speed at which PBC triggering occurs. The coupling speed was increased for each subsequent test until the PBC triggered. The coupling speeds targeted for the test were 2 mph, 4 mph, 6 mph, 7 mph, 8 mph, and 9 mph. The coupling speed at which the PBC triggered was 9 mph. The damage observed resulting from the coupling tests is described. Prior to the tests, a lumped-mass model was developed for predicting the longitudinal forces acting on the equipment and couplers. The test results are compared to the model predictions. Next steps in the research program, including future full-scale dynamic tests, are discussed.

Research to develop new technologies for increasing the safety of passengers and crew in rail equipment is being directed by the Federal Railroad Administration’s (FRA’s) Office of Research, Development, and Technology. Crash energy management (CEM) components which can be integrated into the end structure of a locomotive have been developed: a push-back coupler and a deformable anti-climber. These components are designed to inhibit override in the event of a collision. The results of vehicle-to-vehicle override, where the strong underframe of one vehicle, typically a locomotive, impacts the weaker superstructure of the other vehicle, can be devastating. These components are designed to improve crashworthiness for equipped locomotives in a wide range of potential collisions, including collisions with conventional locomotives, conventional cab cars, and freight equipment. Concerns have been raised in discussions with industry that push-back couplers may trigger prematurely, and may require replacement due to unintentional activation as a result of service loads. Push-back couplers are designed with trigger loads meant to exceed the expected maximum service loads experienced by conventional couplers. Analytical models are typically used to determine these required trigger loads. Two sets of coupling tests are planned to demonstrate this, one with a conventional locomotive equipped with conventional draft gear and coupler, and another with a conventional locomotive retrofit with a push-back coupler. These tests will allow a performance comparison of a conventional locomotive with a CEM-equipped locomotive during coupling. In addition to the two sets of coupling tests, car-to-car compatibility tests of CEM-equipped locomotives, as well as a train-to-train test are also planned. This arrangement of tests allows for evaluation of the CEM-equipped locomotive performance, as well as comparison of measured with simulated locomotive performance in the car-to-car and train-to-train tests. The coupling tests of a conventional locomotive have been conducted, the results of which compared favorably with pre-test predictions. In the coupling tests of a CEM-equipped locomotive, the coupling speed for which the push-back coupler (PBC) triggers will be measured. A moving, CEM-equipped locomotive will be coupled to a standing cab car. The coupling speed for the first test will be low, approximately 2 mph. The test will then be repeated with the speed increasing incrementally until the PBC triggers. This paper describes the fabrication, retrofit, test requirements, and analysis predictions for the CEM coupling tests. The equipment to be tested, track conditions, test procedures, and measurements to be made are described. A model for predicting the longitudinal forces acting on the equipment and couplers has been developed, along with preliminary predictions for the CEM coupling tests.

Research to develop new technologies for increasing the safety of passengers and crew in rail equipment is being directed by the Federal Railroad Administration’s (FRA’s) Office of Research, Development, and Technology. Crash energy management (CEM) components which can be integrated into the end structure of a locomotive have been developed: a push-back coupler and a deformable anti-climber. These components are designed to inhibit override in the event of a collision. The results of vehicle-to-vehicle override, where the strong underframe of one vehicle, typically a locomotive, impacts the weaker superstructure of the other vehicle, can be devastating. The components are designed to improve crashworthiness for equipped locomotives in a wide range of potential collisions, including collisions with conventional locomotives, conventional cab cars, and freight equipment. Concerns have been raised in discussions with industry that push-back couplers may trigger prematurely, and may require replacement due to unintentional activation as a result of service loads. It has been shown analytically that push back coupler trigger loads exceed the service load capacity of conventional couplers and draft gears. Two sets of coupling tests are planned to demonstrate this, one with a locomotive equipped with conventional draft gear and coupler and another with a locomotive equipped with a pushback coupler. These tests allow for comparison of conventional with CEM-equipped locomotive measured performance during coupling. In addition to the coupling tests, car-to-car compatibility tests of equipped locomotives and a train-to-train test are also planned. This arrangement of tests allows for evaluation of the CEM-equipped locomotive performance, as well as comparison of measured with simulated locomotive performance in the car-to-car and train-to-train tests. In the coupling tests of conventional equipment, the maximum coupling speed for which there is no damage to either vehicle will be measured. A moving locomotive will be coupled to a standing cab car. The coupling speed for the first test will be 2 mph, the second test 4 mph, and the tests will continue with the speed incrementing by 2 mph until damage occurs to either vehicle. This paper describes the test requirements and analysis predictions for the coupling tests of conventional equipment. The equipment to be tested, track conditions, test procedures, and measurements to be made are described. A one-dimensional model for predicting the longitudinal forces acting on the equipment and couplers has been developed, along with preliminary predictions for the conventional coupling tests. It is expected that damage will occur for coupling speeds between 6 and 8 mph.

The Office of Research, Development, and Technology of the Federal Railroad Administration (FRA) and the Volpe Center are continuing to evaluate new technologies for increasing the safety of passengers and operators in rail equipment. The results of vehicle-to-vehicle override, where the strong underframe of one vehicle, typically a locomotive, impacts the weaker superstructure of the other vehicle, can be devastating. Crashworthy components which can be integrated into the end structure of a locomotive have been developed to inhibit override in the event of collision. Recent research has resulted in the development of a design concept, including evaluation with finite-element analysis (FEA), fabrication, and component tests. The design concept developed incorporates two key components: a push-back coupler and a deformable anti-climber. Detailed designs for these components were developed and the performance of the designs was evaluated through large deformation dynamic FEA. Test articles were fabricated and dynamically tested to verify their individual performance characteristics. The tests were successful in demonstrating the required performance of the components. Test results were consistent with finite element model predictions of energy absorption capability, force-displacement behavior, and modes of deformation. Work is ongoing to retrofit these crashworthy components onto conventional locomotives and conduct full-scale dynamic impact tests of colliding cars, as well as colliding trains. Service tests will be performed to measure the impact speed at which push-back coupler triggering occurs. Vehicle-to-vehicle tests will be conducted to demonstrate the performance of the crashworthy components working together as an integrated system. The vehicle-to-vehicle tests will also allow an evaluation of the crashworthiness compatibility of a modified locomotive with a range of equipment, including conventional locomotives, cab cars, and freight cars. Train-to-train tests are planned to demonstrate incremental improvement, increased crashworthiness, compatibility, and serviceability. This paper describes the tests that are planned to demonstrate the behavior of these components when they are integrated into the end structure of a locomotive. The tests will demonstrate the in-service and crashworthiness performance of the modified locomotives. This research program endeavors to advance locomotive crashworthiness technology and develop the technical basis for generating specifications for push-back couplers and deformable anti-climbers.

The Federal Railroad Administration’s (FRA) Office of Research and Development is conducting research into the occupied volume integrity (OVI) of passenger railcars. OVI refers to a passenger railcar’s ability to preserve space for passengers and crew during accident loading conditions. The information developed in this research program will form the basis for establishing alternative OVI evaluation procedures. These alternative procedures, in turn, will allow a wider variety of passenger railcar designs to have their OVI evaluated, will provide guidance for applying modern engineering technologies, such as finite element analysis (FEA), and will continue to ensure a level of safety in evaluated vehicles equivalent to conventional evaluation. As part of this research program, two tests and corresponding FEA were conducted on a Budd M-1 passenger railcar that had been retrofitted with crash energy management (CEM) components on both ends. This testing and analysis program was sponsored by FRA and carried out by Transportation Technology Center, Inc. (TTCI), Arup, and the Volpe Center. An 800,000 pound load test was conducted on March 13, 2013 and was intended to elastically deform the car. The data generated during this test were, in turn, used to validate FE models of the M-1 car. The second test was performed on July 17, 2013. This test introduced loads into the occupant volume through its CEM attachment points until the ultimate, or crippling, load was reached. By loading the occupant volume through the CEM components, the test load path is similar to the load path that would be traveled by collision loads during activation of the CEM system. This paper presents the results of the crippling test, discusses the sequence of buckling that was observed to occur in the test, and compares the results of the test with the results from FEA of the test conditions. During the crippling test, the car exhibited a crippling load of 1.1 million pounds. This value is consistent with crippling loads reached by two Budd Pioneer cars that were previously tested in an FRA program. The buckling sequence of the members making up the M-1’s occupant volume were particularly well-captured by strain gages during this most recent test. The load path through the occupant volume and the sequence of progressive buckling of structural members is discussed. Additionally, the presence of existing damage and previously-repaired areas and their likely effects on the crippling behavior of the car are discussed.

The Office of Research and Development of the Federal Railroad Administration (FRA) and the Volpe Center are continuing to evaluate new technologies for increasing the safety of passengers and operators in rail equipment. In recognition of the importance of override prevention in train-to-train collisions in which one of the vehicles is a locomotive, and in light of the success of crash energy management technologies in cab car-led passenger trains, the Volpe Center seeks to evaluate the effectiveness of components that could be integrated into the end structure of a locomotive that are specifically designed to mitigate the effects of a collision and, in particular, to prevent override of one of the lead vehicles onto the other. A research program has been conducted to develop, fabricate and test two crashworthy components for the forward end of a locomotive: (1) a deformable anti-climber, and (2) a push-back coupler. Detailed designs for these components were developed, and the performance of each design was evaluated through large deformation dynamic finite element analysis (FEA). Designs for two test articles that could be used to verify the performance of the component designs in full-scale tests were also developed. The two test articles were fabricated and dynamically tested by means of rail car impact in order to verify certain performance characteristics of the two components relative to specific requirements. The tests were successful in demonstrating the effectiveness of the two design concepts. Test results were consistent with finite element model predictions in terms of energy absorption capability, force-displacement behavior and modes of deformation.

This research program was sponsored by the Federal Railroad Administration (FRA) Office of Research and Development in support of the advancement of improved safety standards for passenger rail vehicles. FRA and the Volpe National Transportation Systems Center (Volpe Center) have conducted a research program to develop alternative methods for demonstrating occupied volume integrity (OVI) of passenger rail cars using a combination of testing and analysis. Previous publications have addressed the planning and progress of a series of tests intended to examine the collision load path through the occupant volume of passenger cars equipped with crash energy management (CEM) systems. This program has included an elastic 800-kip buff strength test, two quasi-static tests that loaded a passenger car to its ultimate (crippling) capacity, and corresponding finite element (FE) analyses of each test. This paper discusses the two crippling tests and the companion FE analyses. One alternative method for evaluating OVI moves the applied loads from the line of draft to the collision load path. This alternative methodology also permits a combination of testing and analysis to be used to demonstrate the car’s OVI, in contrast to the conventional methodology (as prescribed in existing FRA regulations) which only permits testing. The alternative methodology was adopted as the recommendations developed by the Railroad Safety Advisory Committee’s (RSAC) Engineering Task Force (ETF) in its “Technical Criteria and Procedures for Evaluating the Crashworthiness and Occupant Protection Performance of Alternatively-Designed Passenger Rail Equipment for Use in Tier I Service.” The research program was undertaken to verify the efficacy of using a combination of elastic testing and plastic analysis to evaluate the OVI of a passenger car loaded along its collision load path as prescribed in the ETF report. Earlier in this research program an elastic test of a Budd Pioneer car was used to validate an FE model of the car, per the ETF’s procedures. This model was then modified to reflect the condition of the car in its crippling test configuration. The model was used to simulate the crippling behavior of the car, following the ETF’s procedures. Two Pioneer cars were then tested to crippling to provide additional data to validate the FE model and the proposed alternative OVI evaluation. Because the test cars used in this research program were equipped with CEM systems, the alternative evaluation loads were placed at the locations where the energy-absorbing components attached to the occupant volume. During both crippling tests, loads were measured at each energy-absorber support location on the live and restrained ends of the car. Additional instrumentation used in the second crippling test included strain gages on the major longitudinal structural members, displacement transducers at each load location, and vertical, lateral, and longitudinal displacement transducers on the underframe of the car. The results of the FE analysis compare favorably with the results of the crippling tests. In particular, the crippling loads are consistent between the tests and analysis: crippling loads for the first and second cars tested were 1.15 and 1.19 million pounds respectively, and the pre-test FEA estimated a crippling load of 1.19 million pounds. The research program has established a technical basis for the alternative OVI requirements and methodology.

The Federal Railroad Administration (FRA) and the Volpe Center are continuing to evaluate new technologies for increasing the safety of passengers and operators in rail equipment. In recognition of the importance of override prevention in train-to-train collisions in which one of the vehicles is a locomotive, and in light of the success of crash energy management technologies in cab car-led passenger trains, the Volpe Center seeks to evaluate the effectiveness of components that could be integrated into the end structure of a locomotive that are specifically designed to mitigate the effects of a collision and, in particular, to prevent override of one of the lead vehicles onto the other. This paper provides preliminary results of a research program that aims to develop, fabricate and test two crashworthy components for the forward end of a locomotive: (1) a deformable anti-climber, and (2) a push-back coupler.

This paper describes the results of quasi-static and dynamic tests of a new shock energy absorber (SEA) capable of high energy absorption while limiting peak dynamic force magnitude in the event of an impact or collision. The SEA utilizes the unique reversible phase transition behavior of Ultra High Molecular Weight Poly-Ethylene (UHMWPE) material under pressure. A prototype drop hammer test confirmed the device’s high energy absorption as well as high damping capabilities at a relatively high deformation rate. The results of the test were used to calibrate a finite element (FE) model that enabled scalability of the SEA for practical applications. Preliminary design and FE simulations were made under a Federal Railroad Administration (FRA) sponsored program toward using a set of SEA as a part of a crash energy management (CEM) system to improve locomotive crashworthiness. The main objective of the program was to prevent locomotive override in the event of an inline collision with a hopper car consist at a closing speed of 30 mph. The FE model, without CEM, was validated to a previously performed full-scale locomotive crashworthiness test at Transportation Technology Center, Inc. (TTCI), Pueblo. The FE simulation results with added CEM system showed successful prevention of locomotive override up to 32.1 mph collision speed. Further scope of using suitably tailored SEA units as buffers to the ends of passenger coaches and tank cars with the objective of enhancing their crashworthiness is discussed.

This paper describes the conduct of the first of a series of quasi-static compression tests of rail passenger equipment being done to examine occupant volume strength. Specifically, this program is investigating methods of evaluating occupant volume integrity when loads are placed along the collision load path of the occupant volume. Budd Pioneer car 244 has been chosen as the test article to examine alternative occupant volume loading strategies. Since this car has been involved in several impact tests as part of a previous research program, it is important to verify the structural integrity of the vehicle before conducting an alternative loading test. Although the vehicle has been modified with crash energy management crush zones at both ends, the occupant volume between the body bolsters is unmodified from the original structure. The 800,000-pound compressive strength test will be used to ensure the structural integrity of the car is intact. Before the conduct of this test, repairs were made to the crush zone. These repairs included replacement of trigger elements in the form of shear bolts and shear rivets. Additionally, energy absorbing elements were removed from the pushback coupler and primary energy absorbers because they would not contribute to the load path of this test. Steel blocks were added to the sliding sill element, enabling it to contact the fixed sill and enhancing the load-bearing capacity of the sliding-fixed sill connection. Preliminary results of this test include an overall description of the test procedures, discussion of permanent deformation observed during the test, and presentation of finite-element simulation results. Detailed analysis of test results, including strain gage data, is ongoing. The test results are being compared with the finite-element model results in support of the next tests planned for this series. The next two tests will evaluate the carbody when it is loaded along its collision load path to establish the elastic limit and crippling strength.

The paper sets out to consolidate relevant learning from South Africa’s two electric heavy haul operations, and relate it to practices in two significant heavy hauling countries, the US as font of heavy haul, and China that has established a significant presence in heavy haul. In comparing the present dominant diesel heavy haul with electric heavy haul, it is evident that the latter can offer sustainability through open system interaction with its environment. However, electric heavy haul solutions are still divergent, contrary to what one would expect in a globalized industry. Reviewing prospects for consideration leads to a main conclusion that future heavy haul electrification should rest on an open system approach within a smart total energy management paradigm.

In support of the Federal Railroad Administration’s (FRA) Railroad Equipment Safety Program, tests have been conducted on prototype commuter rail passenger seats which have been designed for improved occupant protection during commuter train accidents. Quasi-static tests were conducted to evaluate the moment versus rotation behavior of the seat back and to improve the fidelity of the finite element seat model. Dynamic sled tests were conducted with instrumented Hybrid III anthropomorphic test devices (ATDs) to evaluate occupant protection under collision conditions and to improve the fidelity of seat/occupant computer models. The three-passenger prototype seats were designed to meet the following dynamic test requirements: 1. Seats must remain attached to the test fixture. 2. Occupants must be compartmentalized between seat rows. 3. Injury criteria for the head, chest, neck and femur must be within tolerance thresholds specified by the automotive industry. 4. All seat components, including seat cushions, must remain attached. Test conditions were specified for two dynamic sled tests as follows: three forward-facing 50 th percentile male Hybrid III ATDs subjected to an 8G, 250 millisecond triangular crash pulse; and three rear-facing 50 th percentile male Hybrid III ATDs subjected to a 12G, 250 millisecond triangular crash pulse. The 8G crash pulse is specified in the existing American Public Transportation Association (APTA) Standard for Row-to-Row Seating in Commuter Rail Cars [1] and in the Federal Code of Regulations 49 CFR 238.233 [2], and represents nominal collision conditions. The 12G crash pulse represents the collision environment measured in the cab car during a previous full-scale train-to-train impact test of passenger rail cars incorporating crash energy management [3, 4]. The final test results indicate that all test requirements were met: the seats remained attached to the test sled; the ATDs were compartmentalized; all the injury criteria were within accepted tolerance thresholds; and all the seat cushions remained attached.

Previous work has led to the development of a crash energy management (CEM) system designed to distribute crush throughout unoccupied areas of a passenger train in a collision event. This CEM system is comprised of crush zones at the front and rear ends of passenger railcars. With a consist made up of CEM-equipped cars, the structural crush due to a collision can be distributed along the length of the train, crushing only unoccupied areas and improving the train’s crashworthy speed as compared with a conventional train in a similar collision. This paper examines the effectiveness of one particular CEM system design for passenger rail cars. The operating parameters of the individual components of the CEM system are varied, and this paper analyzes the effects of these variations on the behavior of the consist during a collision. The intention is to determine what modifications to the components, if any, could improve the crashworthiness of passenger railcars beyond the baseline CEM design without introducing new hazards to passengers. A one-dimensional, lumped-mass model of a passenger train impacting a heavy freight train was used in this investigation. Using this model of a collision, the force-crush behavior for each end of each car in the impacting consist was varied. The same force-crush characteristic was applied to each car end on the passenger train. The four components of the CEM system investigated were the draft gear, pushback coupler, primary energy absorbers, and occupied volume of the train car. The paper presents selected parameters of particular interest, such as the strength ratio of the primary energy absorber to the pushback coupler and the average strength of the occupied volume. The objective of this work was to ascertain the sensitivities of the various parameters on the crashworthy speed and to help optimize the force-crush characteristic. This investigation determined that modifications could be made to the baseline characteristic to improve the train’s crashworthy speed without creating new hazards to occupants.

Rail vehicle safety standards for the United States have historically placed emphasis on static structural strength requirements to ensure safety. The primary requirements to ensure crash safety of light rail vehicles were static load cases including car body buff loads, collision post loads, corner post loads, etc. More recent developments for light rail vehicles in the United States have included crash energy management design methodologies. This is consistent with the trend in other modes of transportation applying modern crashworthiness engineering. The challenges of incorporating crash energy management into light rail vehicles are the lack of crashworthiness standards for the light rail industry, the introduction of new design methodologies, and the concerns of compatibility of new and older equipment. This issue of compatibility in vehicle designs would often inhibit introduction of innovations and potential safety improvements within an existing light rail transit system. However, there are ongoing efforts to address each of these challenges. The American Society of Mechanical Engineers has a committee working on the development of a new safety standard for light rail vehicles. Light rail vehicle manufacturers are increasingly using modern crashworthiness design principles. In addition, modern crash analysis methodologies allow for the assessment of vehicle incompatibilities in the design process. In this paper, the developments of crash energy management strategies in the light rail industry are discussed. These include the ongoing standards development efforts and the application of crash energy management principles in recent light rail vehicle design efforts. Examples will be provided for the use of crash analyses in a vehicle design. The interaction of the crash and static analyses will be discussed and examples of both compatible and incompatible collision scenarios will be presented.

On March 23, 2006, a full-scale test was conducted on a passenger train retrofitted with newly developed cab and coach car crush zone designs. This test was conducted as part of a larger testing program to establish the degree of enhanced performance of alternative design strategies for passenger rail crashworthiness. The alternative design strategy is referred to as Crash Energy Management (CEM) where the collision energy is absorbed in defined unoccupied locations throughout the train in a controlled progressive manner. By controlling the deformations at critical locations, the CEM train is able to protect against two very dangerous modes of deformation: override and large scale lateral buckling. The CEM train impacted a standing locomotive-led train of equal mass at 30.8 mph on tangent track. The interactions at the colliding interface and between coupled interfaces performed as designed. Crush was pushed back to subsequent crush zones, and the moving passenger train remained in-line and upright on the tracks with minimal vertical and lateral motions. This paper evaluates the functional performance of the crush zone components during the CEM test. The paper discusses three areas of the CEM consist: the leading cab car end, which interacts with a standing locomotive; the coupled interfaces, which connect the CEM non-cab end; and the trailing cab car end, which interacts with the attached trailing locomotive. The paper includes a description of the crush zone features and performance. The pushback coupler must absorb energy in a controlled progressive manner and prevent lateral buckling by allowing the ends of the cars to come together. The deformable anti-climbers are required to resolve non-longitudinal loads into planar loads through the integrated end frame while minimizing the potential for override. The energy absorbers must absorb energy in a controlled progressive manner. The engineer’s space must be preserved so that the engineer can ride out the event. The passenger space must be preserved so that the passengers can ride out the event. The prototype CEM design presented in this paper met all the functional design requirements. This paper describes how the crush zones perform at three different interfaces. Areas for potential improvements include the design of the primary energy absorbers, the placement of the engineer’s compartment, and the interaction between the last coach car and the trailing locomotive.

In conjunction with full-scale equipment tests, collision dynamics models of passenger rail cars have been developed to investigate the benefits provided by incorporating energy-absorbing crush zones at the ends of the cars. In a collision, the majority of the structural damage is generally focused at the point of impact for cars of conventional design. In contrast, cars with crush zones, or crash energy management (CEM), can better preserve occupied areas by distributing crush to the ends of cars. Impact tests of conventional equipment have already been conducted, which consisted of a single car and two coupled cars colliding with a rigid wall. Corresponding tests are planned using CEM equipment. This paper presents preliminary predictions of the one- and two-car CEM tests, and compares them to the results of the respective conventional equipment tests. The comparison will focus on loss of occupant volume, secondary impact velocity (SIV), and lateral buckling, as measures of occupant protection. The modeling results indicate that the occupant volume can be preserved in both the one-car and two-car tests of the CEM equipment, while 2 1/2 and 3 feet of occupant volume were crushed in the respective tests of conventional equipment. In the two-car model, the CEM design is able to distribute the crush between both cars, whereas the conventional design incurs nearly all the crush at the point of impact. The CEM design can absorb more energy without crushing the occupied area because it requires a higher average force per foot of crush at the vehicle ends. The trade-off associated with this higher crush force is generally a higher SIV for occupants in the CEM cars. Secondary impact velocity refers to the velocity at which an occupant strikes some part of the interior, in this analysis the back of the seat ahead of the occupant. The greatest SIV penalty is in the impacting car. The difference between the SIV for cars in a conventional and a CEM consist decreases in each trailing car. That is, the SIV generally decreases in each trailing car of a CEM consist, while the SIV remains approximately the same in each trailing car of a conventional consist.

On December 3, 2003, a single-car impact test was conducted to assess the crashworthiness performance of a modified passenger rail car. A coach car retrofitted with a Crash Energy Management (CEM) end structure impacted a fixed barrier at approximately 35 mph. This speed is just beyond the capabilities of current equipment to protect the occupants. The test vehicle was instrumented with accelerometers, string potentiometers, and strain gages to measure the gross motions of the car body in three dimensions, the deformation of specific structural components, and the force/crush characteristic of the impacted end of the vehicle. The CEM crush zone is characterized by three structural components: a pushback coupler, a sliding sill (triggering the primary energy absorbers), and roof absorbers. These structural mechanisms guide the impact load and consequent crush through the end structure in a prescribed sequence. Pre-test activities included quasi-static and dynamic component testing, development of finite element and collision dynamics models and quasi-static strength tests of the end frame. These tests helped verify the predicted structural deformation of each component, estimate a force-crush curve for the crush zone, predict the gross motions of the car body, and determine instrumentation and test conditions for the impact test. During the test, the passenger car sustained approximately three feet of crush. In contrast to the test of the conventional passenger equipment, the crush imparted on the CEM vehicle did not intrude into the passenger compartment. However, as anticipated the car experienced higher accelerations than the conventional passenger car. Overall, the test results for the gross motions of the car are in close agreement. The measurements made from both tests show that the CEM design has improved crashworthiness performance over the conventional design. A two-car test will be performed to study the coupled interaction of CEM vehicles as well as the occupant environment. The train-to-train test results are expected to show that the crush is passed sequentially down the interfaces of the cars, consequently preserving occupant volume.

Crash energy management (CEM) is a type of equipment design that is intended to protect occupant space during a collision. Structures at the front and back of each car act as crumple zones that absorb the collision energy. CEM is intended to distribute the damage from a collision throughout a consist to unoccupied areas. This paper describes how factors that vary in the operation of passenger trains affect the crashworthiness performance of conventional and CEM trains. Crush and secondary impact velocity are introduced as measures of crashworthiness performance. The collision scenario selected for this study includes a standing locomotive-led freight train and a cab led passenger train with an initial velocity. The passenger train contains either all CEM or all conventional equipment, and is either a multiple unit (MU) train with no locomotive, or push-pull train. The influence of consist type (MU or push-pull,) car weight, and the number of cars in a train-to-train crashworthiness are explored. The crashworthy speed is that speed at which all of the passenger train occupants are predicted to survive in the selected collision scenario. For both conventional and CEM equipment, MU trains have slightly higher crashworthy speeds than push-pull trains. Trains with heavier cars have lower crashworthy speeds for both conventional and CEM equipment. Longer trains also have lower crashworthy speeds, although the decrease crashworthy speed is less for CEM trains than for conventional trains. In all cases evaluated, the CEM trains have significantly higher crashworthy speed than the conventional trains; the crashworthy speed of CEM trains is typically twice that of conventional trains, and in some cases is nearly three times greater.