Structural Crashworthiness of Railway Vehicles

Manuel S. Pereira1

1IDMEC, Department of Mechanical Engineering, Instituto Superior Técnico, Technical University of Lisbon, Avenida Rovisco Pais 1049-001 Lisbon, PORTUGAL, mpereira@dem.ist.utl.pt

Abstract

As a form of transport, rail has always maintained lower accident levels than its counterparts, the car and the airplane. The railway industry, however strives for still better safety measures to be implemented – a fact which intensifies with each accident that occurs. In the last years the continuous developments in technology, computer modeling capabilities and know-how have opened up various research activities in the passive safety area, also known as crashworthiness.

Whereas the objective of active safety systems (such as signalling and automatic train protection systems) is to avoid accidents, passive safety only comes into effect in the event of collision and its objective is to significantly reduce the severity of accidents.

Rail vehicles can be designed to behave in ways that minimize the injuries of passengers and crew during collisions. Crashworthy vehicles contain in-built design features, which are not relevant in normal train operations, but protect the train occupants should an accident occur. A methodology has been developed within the projects TRAINCOL, SAFETRAIN and SAFETRAM for improved passive safety in railway transportation. This methodology includes:

i) A review of past accidents, identification of reference collision scenarios and evaluation of their consequences. Risk assessment for improved passive safety was also considered;

ii) The establishment of a set of reference collision scenarios for main line train and city tram operations. Together with statistical and risk analysis, design feasibility studies played a major role in the definition of the reference scenarios;

iii) The development of a general framework for structural crashworthiness design train and in city and periurban tram vehicles and

iv) Guidelines for design validation procedures through modeling, component and real size dynamic testing.

Improved passenger and crew safety issues have been systematically addressed. Passenger and crew accommodations on a number of railways within Europe have been reviewed from the standpoint of interior safety. Conclusions about typical acceleration pulses and appropriate values of injury criteria for the railway industry have also been established.

One of the most important achievements of these projects was then to demonstrate the feasibility of optimized carbody structures to present an improved safety level to occupants, within acceptable cost and masses for the defined construction solutions. A European Standard is now being completed providing the framework for determining the crash conditions that railway vehicle bodies should be designed to sustain based on the most common accidents and associated risks. It also defines suitable passive safety features to meet the requirements.

Introduction

Occupant safety is dependent on the configuration and severity of the accident, as well as the degree of crashworthiness engineered in the overall vehicle design. Train vehicle occupant survivability in a given crash scenario is a function of the kinematic behavior of the entire train set, the integrity and collapse characteristics of the structure of each vehicle and the overall interior configuration of a compartment and occupant/surfaces contact characteristics.

Train crash events can be basically depicted into two phases: In a first phase, normally referred to as primary collision, the initial kinetic energy is progressively dissipated by means of plastic structural deformation resulting from the crash generated impact loads. In this phase occupant compartment integrity and acceptable vehicle acceleration levels are the most important design requirements to be considered. In a second phase, normally referred to as secondary collision, the occupant will be subject to a great variety of potentially harmful occupant/interior or occupant/occupant contacts. Design requirements must involve the aspects of interior layouts, acceptable severity levels and biomechanical response to vehicle crash pulses. The friendliness of the compartment interior is obviously a major design issue.

The energy generated in train collisions has to be dissipated by plastic crushing of designated structural arrangements developing forces, which in turn cause decelerations, which are directly responsible for the severity of secondary collisions. These designated structural arrangements are normally located at the extremities of the vehicles and are designed to absorb maximum possible energy and collapse in a controlled manner preserving the occupant compartment integrity. The crushable zones must be confined to reasonable lengths and the range of crush loads are to be consistent with passenger compartment buckling loads and static specified buffer loads [9].

Train collision are always assumed to occur under fully plastic impact conditions, which means that after collision both sets have the same velocity, which corresponds to a zero coefficient of restitution.

For single vehicle collisions, such as the case of many tram configurations, the starting point for design requires the knowledge of the design collision scenario speed and the maximum allowed acceleration experienced by the occupant compartment. Closed form solutions are available for determining the required crushing length. Forces can subsequently be determined to specify the design requirements, in terms of a force-displacement curve for the extremities.

For train collisions involving several vehicles the problem is considerable more complex. The energy distribution along train sets is strongly dependent on:

• Train configuration, namely the number of vehicles • Mass distribution – masses of individual vehicles along the train set • Collision speed • Type of scenario.

The characteristics of structural crashworthy vehicles are expressed in terms of force-displacement curves with different levels of plastic loads. Different force-displacement curves are used for inter-rake and inter-trailer zones and are referred to as EE and IE ends, respectively.

SAFETRAIN project [2], [3] and [11] concentrated in the study of regional, intercity and high speed train sets configurations. SAFETRAM project [12] dealt with the specificities of city trams and periurban trams.

Based on results of these projects, methodologies for improved passive safety, including the specification, design, testing and validation procedures for crashworthy rail vehicles, is outlined. Specific recommendations are proposed for passive safety development, minimisation of loss of survival space, train energy management issues, vehicle design, minimisation of severity of occupant injuries, methods of validation of crashworthy designs, static and dynamic testing and structural and passenger/crew numerical simulations.

Review of accidents and choice of representative collision scenarios

The principal aim of this task is to define the representative collision scenarios, their characteristics and parameters to be applied for modelling, design and test of crashworthy structures and other protection means (anti-overriding devices, obstacle deflectors, interior design). The main characteristics of collision accidents in Europe have been gathered into a representative database [8]. The quantity of data collected corresponds to approximately 60% of total European railway production (in terms of train kilometres, passengers transported, passenger kilometres and length of lines in service). The database forms a statistical population of collision accidents over the five years 1991 to 1995.

The analysis showed that building practicable levels of energy absorption into passenger rolling stock would improve the passive safety of vehicles in head on collisions, rear on collisions, collisions with cars and lorries on level crossings and collisions with buffer stops.

Risk analysis on the city tram accident data, collected through an inquiry was performed [5]. The purpose of the LRV statistics study was to identify relevant collision scenarios including an evaluation of their consequences, in terms of material damage and injuries and fatalities as applied to city tram operations. As there are few periurban trams in service and periurban traffic is relatively recent, all analysis refers to accident data involving only regional traffic. Risk and statistical analysis was conducted on the German and French accident data of ERRI B205 database, involving 248 and 329 accidents, respectively [10].

Based on the findings of the statistical analyses described herein the scenarios and train and tram configurations, presented in table1, have been selected.

Rollling stock

Collision scenarios Configurations

Trains S1) Train vs. train S2) Train vs. buffer stops S3) Train vs. deformable obstacle In level crossing different statistical impact velocities were defined from the B205 data base analysis. Each velocity covers, respectively, 70, 80 and 90 % of accidents occurred. For scenario 1 : V70% = 30 km/h, V80% = 40 km/h, V90% = 55 km/h. For scenario 3 : V70% = 80 km/h, V80% = 100 km/h, V90% = 120 km/h.

train types were identified in single (multiple) units. Type A – Main line train – mass 340 t – 8(16) vehicle train sets Type B – Main line train – mass 412 t – 8(16) vehicle train sets Type C – Regional train - mass 129 t – 3(6) vehicle train sets Type D – Motor coach, single vehicle – mass 50 t 1(2) vehicle train sets

City trams

C1) Emergency braking. Not applicable in this analysis C2) Collision with an identical city tram. 20 km/h C3) Collision against a light rigid truck (3t). 30 km/h C4) Collision against a 55 t periurban tram with appropriate compatibility. 12 km/h

Multiple-articulated tram configurations Masses of 20, 35 and 45 t.

A crushing length of 0.5 m is assumed and based on the assumptions of a buffer load of 200kN Compressive force reaches a maximum of 470kN

Peri urban trams

P1) Collision against a rail vehicle (80 t freight wagon with UIC 526-1 buffers). 25 km/h P2) Collision against a regional train (129 t train). 23 km/h. P3) Collision against an identical periurban tram. 36 km/h

P4) Collision against a 16.5 t rigid truck on level crossing. 40 km/h

The periurban tram is also multiple-articulated Mass of 55 t. A crushing length of 0.7 m is assumed and based on the assumptions of a buffer load of 600kN Compressive force reaches a maximum of 1400kN.

Table 1: Collision scenarios and train and tram configurations

Design feasibility and optimization studies for train set configurations

Geometrical characteristic of the extremities were fixed identical for the different trains: Driver’s cabin:

Total crush length available is 1900 mm, Tolerated crushing length of the driver’s cabin: 1000 mm, Component (non structural devices) crushing length in front of the cabin: 800 mm Coupler crushing length 100 mm.

Intertrailer: Inter-trailer length: 800 mm Coupler crushing length: 200 mm Component (non structural devices) crushing length at the inter-trailer: 200 mm Crushing length of the structure at the inter-trailer: 500 mm

Safety objectives were established in terms of mean accelerations below 5g in the passenger compartment and no permanent deformation should occur in the passenger area.

Optimisation procedures have been applied to trains type A, B, C and D. In all cases and for all collision scenarios the proposed crashworthy train design with the optimised plastic load levels respect the acceleration criteria and the limits in the levels of deformation. The extremities so determined should ensure no deformation in passenger areas for a collision speed of 55 km/h in scenario 1 (train vs. train) and 100 km/h in scenario 3 (train vs. lorry in level crossing). The obtained optimal force-displacement curves result in decelerations in the passenger areas, which are below 5g. The resulting force-displacement curves for the HE and LE ends are represented in figure 1.

Fig. 1: HE and LE end characteristics for train C

Table 2 summarizes the general requirements in terms of energy absorption for the most critical scenarios:

Train Scenario 1 Scenario 3 M=16.5 t

Type Mass V (km/h) E1 (MJ) E2 (MJ) V (km/h) E1 (MJ) E2 (MJ) A 340 t 55 3.6 2.7 96 5.0 0.7 B 412 t 55 2.95 2.8 96.5 4.9 0.7 C 129 t 55 2.3 1.4 98 4.6 0.6 Notes: Scenario 1 and Scenario 3 – Reference Accident Scenarios

E1 – Energy absorbed in the front end E2 – Energy absorbed in the inter-trailer areas

Table 2: Energy levels for train collisions

Design feasibility and optimization studies for tram configurations

For all the scenarios, the allowable consequences of the accidents are:

• Plastic deformation only in localized crash-zones, not affecting the survival space of the occupants.

• Minor injuries for the tram occupants. As reference, a 5g maximum deceleration of the car body is assumed.

Using the SELFA plots [6] methodology the analysis of design feasibility involves the following steps:

1. From the energy-force curves energy values associated with the maximum force levels are found in the appropriate curve for the available crush length.

2. Equivalent masses can also be found depending on the masses of the city or periurban tram and the colliding partner.

3. Using the energy levels and the equivalent mass previously calculated the maximum allowable speed is then obtained.

Table 3 summarises the results for design feasibility.

City Trams (35 t) Periurban trams (55 t) Scenario Force

(kN) Energy

(MJ) Meq (t)

Speed (km/h) Scenario Force

(kN) Energy

(MJ) Meq (t)

Speed (km/h)

City Tram (2) 470 .290 35 20 80 t wagon (6) 1400 .8 65.2 25 3 t truck (1) 470 .145 5.5 30 129 t train (7) 1400 .9 77.1 23

470 .145 42.8 12 Periurban (5) 1400 1.6 55.0 36 Periurban (3) 16.5 lorry (4) 1400 .8 25.4 40

The numbers in bracket refer to numbered points in the energy-mass plots in the 1st quadrant of figure 1.

Table 3: Energy absorption characteristics and allowable speeds for trams and periurban trams

Overriding studies

A review of accident data within Europe and the USA has highlighted that end-on collisions (head to head or rear-on collisions) are responsible for most of the serious and fatal injuries to passengers and crew in train accidents. Within these reviews, vehicle overriding has been identified as one of the most important

factors in determining the number and severity of injuries; it has been demonstrated that the casualty rate, especially fatality rate increases if overriding occurs. It is evident therefore that override prevention will significantly improve passenger and crew safety on the European rail network. Before this can be achieved, however, a thorough understanding of the causes of overriding is necessary.

The study of European accidents produced the following general conclusions.

• If overriding occurs, fatality rate is 3-4 times higher than for similar collisions without overriding. Most fatalities are in the overridden vehicle.

• Fatalities occur in 70% of all overriding collisions.

• With buffered stock, overriding can occur at closing speeds as low as 15 km/h.

• Overriding may occur at collision energies as low as 2.5MJ but becomes likely at collision energies greater than 10MJ.

• Collisions involving vehicles with buffers are approximately three times more likely to result in override than collisions without buffers.

• There is no evidence to suggest vehicle pitch contributes to overriding in passenger vehicles.

2D multibody models have been developed to study overriding effects in train collisions [1] and [4]. These models include: bogie arrangements with primary and secondary suspensions with rigid stops; representation of structural and non-structural devices behaviour in the longitudinal direction; flexibility of passenger cars; contact capabilities between anti-climbers.

A series of scenarios have been considered including train types A, B and C. For each case three collision speeds have been studied. Favourable comparison of results also indicates that the overriding phenomena and pitching motions, in general, do not affect the basic mechanisms of energy absorption as depicted by 1D models.

Major conclusions from this study are:

• Vertical gaps and vertical forces tend to increase for interfaces away from the inter-train areas. • Maximum values tend to increase with collision speed.

• Maximum values of vertical gaps are around 100-140 mm. However, over riding phenomena in middle train cars is typically initiated with vertical gaps of around 50 mm.

• Vertical forces have been found to reach values as high as 150 kN. These force levels indicate that the deformation behaviour of anti-climbers, in the vertical direction, must be subject to careful design, and provisions must be taken to accommodate some energy absorption with reduced force levels, in the vertical direction.

• Overall results indicate that the dynamics of overriding is strongly dependent on: Vertical anti-climber crushing behaviour; Suspension characteristics with emphasis in jounce stop strokes; Center of mass offsets; Collision speeds.

• And it is less dependent on rain configurations

Overriding in end-on collisions is the single most serious event that can happen as far as safety of passengers is concerned. Surfaces, which can easily deform or slide over one another, e.g. buffers, are instrumental in allowing vertical forces to develop which initiate override. The project proposed a draft specification for anti-climbers for discussion purposes.

A final point that requires consideration is the inter-operability of rolling stock throughout Europe. Currently there are several designs of anti-climbers, each of which is incompatible with the other. If the safety of passengers and crew is to be increased by the prevention of overriding, serious consideration needs to be given to specifying a common design of anti-climber fitted to all vehicles in the same way that buffer position has been specified in the past.

Design, modelling and testing of rail vehicle ends

In the initial stages of the SAFETRAIN project the technical feasibility of initial designs of new energy absorption zones located at the train ends (HE) and at the ends of intermediate vehicles of the train (LE) was appraised. Global design and test specifications have been established for regional type trains. This case was considered as most challenging, in view of the foreseen small space available for the HE and LE extremities (1.8m and .7m, respectively). The levels of energy required to be absorbed in these extremities were 4.6 MJ and 0.7 MJ, respectively. General construction rules were issued concerning loading gauge, lengths of high and low energy ends, window and door position, and type of coupler, obstacle deflector and anti-climbers. The design of the HE and LE extremities was carried out completed and dully validated with appropriate detailed FE model. Components and sub-assemblies were manufactured and tested dynamically before full scale manufacturing of the HE and LE extremities.

HIGH ENERGY END

In the high-energy end it was originally intended that all deformation would occur forward of the driver’s accommodation. However, since the design was for regional trains, where the length of trains is limited by platform length, it was established that part of the driver’s accommodation would be used for structural energy absorption. A survival space for the driver would be maintained at the rear of the cabin. In order to demonstrate that there would be sufficient survival space for the driver, a driving console and a sliding seat were fitted to the structure to be used in the real size dynamic crash test. The console played no part in the energy absorption. The net outcome of these modifications did not change the force-displacement and was that the structure would easily meet the 4.6 MJ requirements.

LOW ENERGY END

Although the vehicle end was designed to collapse in a controlled manner and be energy absorbing, the required 0.7MJ was to be absorbed in phases 1 and 2 only. The general layouts of the manufactured extremities are shown in figure 2.

Figure 2: High energy and low energy extremities

MODELLING AND DYNAMIC TEST VALIDATION

The Finite element models are shown in figure 3.The HE end was modelled using ANSYS 5.5.3 to construct the model and RADIOSS 4.1 to carry out the numerical analysis. The dynamic impact was modelled by simulating a wagon of mass 46250kg, to which the extremity is attached, impacting a stationary wagon of mass 44900kg at 20m/s or 72km/hr.

The numerical analysis of the low-energy end was undertaken using PAMCRASH 98 software. The model was attached to a rigid wall and impacted with a rigid heavy plate (5 m/s for the case of the non structural device and 4 m/s for the deformable structure). Advantage was taken of symmetry and only half the structure was modelled. The objective of the dynamic tests was the validation of methods of controlled deformation and energy absorption for different vehicle types and the preparation of detailed measurement specifications required for assessment of vehicle crashworthiness. The dynamic test depicted in figure 3 involves two test vehicles with 45 t each colliding at a speed of 73.5 km/h generating an energy absorption of 4.6 MJ at the test cabin. The results of the tests have been used for comparison with numerical simulations and static crush test results [7].

Figure 3: Finite element modelling of high and low energy ends

Both quasi-static and dynamic tests allowed validation of the requirements on energy absorption levels and on crushing force level of the front end. Force-displacement and energy curves and energy absorption were in a very good agreement between the numerical simulations and the dynamic tests, as it can be observed from the plots shown in figure 4. Figure 4 also shows a favourable comparison of the crushing evolution as obtained from the dynamic and static tests and the dynamic numerical simulation.

Figure 4: Comparison of tests data: Force-displacement curves and pattern deformations

Design, modelling and testing of tram extremities

Global design and test specifications have been established for city trams and periurban trams.

CITY TRAM

Overriding is prevented as the front end shock absorbers are fitted out with anti climbers made to withstand vertical force 50 kN. The design is proven for misalignment of up to 50 mm.

With respect to scenario C3, anti-intrusion safety must be accomplished by the design and represents another requirement for the structure.

Energy absorption: the test specimen has to provide a progressive characteristic for the energy absorption as displayed. In the first step, reversible devices are used for energies of up to 35 kJ. In this step the trigger peaks shall not exceed the buffer load of 200 kN. The energy absorbers for the second step may get deformed irreversibly, but an easy changeability is required. In contrary to frontal collision scenarios C2 and C4, the carshell structure may be used to absorb some energy in scenario C3 (corner collision with a truck). But the door openings of the entrance area and the survival space shall be maintained.

The maximum deceleration levels are generally less than 3g, for each collision scenario, therefore the design will normally respect the deceleration criteria of a 5g threshold.

Buffing compatibility with respect to collisions with periurban tram must be fulfilled (C4). The height of the impact zone of the collision partners is schematically represented in the figure.

Driver’s visibility : Any obstacles with a height of 1.2 m above the top of the rail, and with a distance of 0.3 m to the front of the vehicle must be visible for the driver.

The survival space for the driver must be maintained. DIN 5560 [14] is relevant to the specification of the survival space. Consequently, one of two criteria must be met after the crash. Either the distance between the driver’s desk and the driver’s seat is 300 mm at a minimum, or the distance between the driver’s desk or the back wall of the cabin is not less than 750 mm.

The coupler arrangement shall not contribute to the energy absorption. The folded coupler is located behind the crash zone.

Figure 5 shows the structural arrangement for the city tram test layer.

Figure 5: Design of the city tram test specimen

For the city tram, the tests and the calibrations on the changeable crash modules at the front of the driver's cabin have been well performed and analyzed involving energy absorption of 135 kJ. Then the test on the mock-up has presented good results for these elements (protection against overriding and crushing process). The corresponding absorber tests have been correlated, precisely for the city tram test design. After the tests, a final correlation has been successfully obtained for the city tram as shown in figure 6.

Figure 6: Validation of the city tram test specimen

PERIURBAN TRAM

Overriding is prevented by using anti-climbers withstanding vertical forces of up to 150kN. Vertical offsets of up to 50 mm are allowed. Compatibility with buffers of freight wagons is assured.

The vehicle shall absorb the energy appropriate to each relevant limiting collision scenario in a controlled manner. This shall be accomplished in such a way that structural collapse is confined to designated areas of the structure and the main passenger/crew space is preserved. The static longitudinal strength of the periurban trams is equal to 600 kN, then the maximum crush force is 1500 kN.

The maximum deceleration levels are generally less than 3g, for each collision scenario, therefore the design will normally respect the deceleration criteria of 5g.

For the periurban trams, an obstacle deflector equivalent to the classic train deflector is not required. Nevertheless, a stone deflector equivalent to the trams deflector is required.

Any obstacles with a height of 1.2 m above the top of the rail and with a distance of 0.3 m to the front of the vehicle must be visible for the driver.

The vehicle shall preserve the survival space and prevent intrusion inside. For the present design the following criteria was adopted: either the distance between the driver's desk and the driver's seat is 300 mm at a minimum, or the distance between the driver's desk and the back wall of the cabin is not less than 750 mm.

The coupler arrangement shall not contribute to the energy absorption, but the design must make sure that the coupler does not disturb the correct functioning of the energy absorbers (in other projects, manufacturers can propose couplers with contribution of the energy absorption). In case of an impact against a train with central coupler, the coupler shall be caught to ensure the energy absorption and prevent intrusion of this last. Space for the installation of a radio system must be provided; therefore the cabin’s floor level must be specified accordingly.

The test specimen is displayed in figure 7. The requirement of a progressive energy absorption in designated collapse zones could be met by the energy absorption concept which is composed of three steps: (1) reversible shock absorber, (2) changeable crash module, (3) main structure. The main structure provides a margin which is not used in the specified scenarios.

Figure 7: Design of the periurban tram test specimen

The simulation effort represented an important part of the design process. The Periurban cab concept is very demanding and was based on a full 3D crush kinematics process involving a complex interrelation of distinct crush processes of A-pillars and the structural devices. Figure 8 compares the crushed test specimen and the numerical simulation results for the periurban test layer.

Several innovative features included in the present crashworthiness concept provide the necessary conditions to meet a specific set of challenging design requirements in terms of the variety of colliding partners and the geometric and loading constraints. Different types of energy absorbers at different heights are provided to meet the requirements which result from the different collision partners.

Figure 8: Validation of the city tram test specimen

Improved passenger and crew safety

The design of vehicle interiors to minimise secondary impact injuries is extremely complex. Whilst many measures, such as preventing a relative velocity build up between the occupant and his surroundings, the provision of “soft edges” etc are obvious, a means of specifying such features is much more difficult. Current specifications within Europe tend to provide a list of aspirations rather than specific requirements. Recent advances in the car industry and in modelling vehicle interiors now allow the rail vehicle interior designer to provide more specific requirements. An assessment of the known acceleration-time pulses in both the rail and motor industry was made with the objective of determining a representative pulse to be used for any future mathematical modelling or sled tests. The study a corridor in which the acceleration pulse must fall, thereby allowing the exact shape of the pulse to be determined by the vehicle designer. The speed change associated with the acceleration corridor is 30 km/h, which covers almost 60% of all head-on collisions, 90% of rear-on collisions and a significant proportion of buffer stop and level crossing collisions.

Agreed injury criteria are recommended to enable seats and tables, in particular, to be modelled and/or tested. Finally, drivers are at extreme risk in collisions. Modelling and test work have indicated mitigation measures, which should significantly enhance their likelihood of survival.

Models representing 5th, 50th and 95th percentile cab occupants have been used to determine the relative benefits of using a seatbelt, airbag and knee bolster in simulated end-on collisions. Both modern European regional train cabs and high density UK cabs with very limited driver space have been modelled. The simulation of passenger impacts with the interior furniture of a railway carriage, specifically with seats, tables and in some scenarios other passengers was carried out for train interior configurations. The results highlight the different requirements for passengers according to the different carriage seat layouts and the sizes of passengers considered in this study.

Figure 9 shows the model used in the analysis of the driver impacts and an example of an occupant impact in a classical train seating arrangement including seat models with structural flexibility.

Figure 9: Driver and passenger models for secondary collisions.

The most significant scenario for CT occupants is the emergency braking (see WP 1), principally for the standing passengers, resulting from the secondary collision of the passengers with the interior feature of the vehicle. As the base of the mean deceleration value for the reference collision scenario, the prescription of 2.73 m/s2 resulting from the German regulation (BO Strab) [14] has been chosen with an operating speed of 70 km/h. Before the occupant modelling, it was necessary to validate the MADYMO HIII standing dummy occupant kinematics and injury severity. A standing dummy conversion kit has been acquired and a sled for specific emergency braking (carriages and platform) has been constructed in INRETS and validated with tests. Different tests have been carried out, on dummies or volunteers, with different deceleration levels, surrounding features, dummy orientations and grip systems.

The European Standard: Railway applications — Crashworthiness requirements for railway vehicle bodies

This standard [15] (prEN 15227:2005) has been prepared by Technical Committee CEN/TC 256 “Railway Applications”, the secretariat of which is held by DIN. This standard is currently submitted to the CEN Enquiry. This standard has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive(s).

This European standard applies to new designs of locomotives and passenger carrying rolling stock as defined in categories C-I to C-IV of clause 4 of the static requirements standard. The design of new vehicles for use in passenger trains is based on operations with compatible rolling stock that also meet this standard.

The requirements apply to the vehicle body, and to those mechanical elements directly associated with it that may be used to absorb energy in a collision, such as couplers, buffing systems, anti-climbers and obstacle deflectors, etc. They do not cover the safety features of doors, windows, system components or interior features except for specific issues relating to the preservation of survival space.

The requirements do not cover all possible accident scenarios but provide a level of crashworthiness that will offer an appropriate level of protection in most eventualities, when the active safety measures have been inadequate. The requirement is to provide a level of protection consistent with the probable collision risks and this is achieved by addressing the most common types of collision causing injuries and fatalities.

The proposed standard prescribes the applicable design collision scenarios and gives guidance on suitable parameter values for use in these scenarios.

The standard identifies common methods of providing passive safety that may be adopted to suit individual vehicle requirements. The standard also specifies the characteristics of reference obstacle models for use in the design collision scenarios. Not all vehicles in a train have to incorporate energy absorption but passenger train configurations formed entirely of new vehicle designs shall, as a whole, comply with this standard.

The standard also specifies the requirements for demonstrating that the passive safety objectives have been achieved by comparison with existing proven designs, numerical simulation, component or full-scale tests, or a combination of all these methods.

To the extent required by this standard the following measures shall be employed to provide protection of occupants in the event of a collision:

- Reduce the risk of overriding

- Absorb collision energy

- Maintain survival space and structural integrity of the occupied areas

- Limit the deceleration

- Reduce the risk of derailment and limit the consequences of hitting a track obstruction

Conclusions

Passive safety in railway transportation deals with means to provide a safe environment for its occupants during identified train collision scenarios. Injuries or deaths are caused by severe occupant/interior contacts, which result mainly from significant damages in the vehicles’ structures or from large decelerations sustained by a vehicle during the crash events.

A methodology has been developed within the projects TRAINCOL, SAFETRAIN and SAFETRAM for improved passive safety in railway transportation. This methodology includes: i) A review of past accidents, identification of reference collision scenarios and evaluation of their consequences. Risk assessment for improved passive safety was also considered; ii) Development of a general framework for structural design in train and tram vehicles and iii) Guidelines for design validation procedures through modeling, static or dynamic testing.

One of the most important objectives of the suite of passive safety European projects was then to demonstrate, for trains, periurban trams as well as for the city trams, the feasibility of optimised carbody structures to present an improved safety level to occupants, within acceptable cost and masses for the defined construction solutions.

New design concepts have been developed by defining technical design requirements to manage the collision energy. Critical vehicle crashworthy validation procedures were carried out including mathematical modelling simulation and component and full scale testing.

The friendliness of the compartment interior is now a major design issue and its treatment will complete the framework of railway passive safety. SAFEINTERIORS, a European project to start now, will present the European railway industry with a key step towards achieving full interoperability by providing the scientific and technological basis to implement a consistent methodology to design, test and validate improved interior solutions, thus reducing the levels of fatalities and injuries in rail accidents.

This new interior passive safety framework will provide a systems approach to drastically reduce injuries and fatalities by combining and exploiting in a cost efficient and optimised manner the already well matured railway structural crashworthiness (closely linked with primary collisions events), with injury biomechanics, directly associated with secondary collisions.

Acknowledgements

The work reported herein was carried out in projects TRAINCOL, SAFETRAIN, SAFETRAM, under the BRITE/EURAM 4th Framework program and the Growth 5th framework program, funded by the European Commission.

The participation in the SAFETRAIN and SAFETRAM consortia of the following partners is acknowledged. Bombardier Transportation, Portugal, S.A., ERRI - Foundation European Rail Research Institute, HOLLAND, SNCF - Direction du Matériel et de la Traction, France, Deutsche Bahn AG GERMANY, PKP - Railway Scientific and Technical Centre, POLAND, AEA Technology, UNITED KINGDOM, Alstom – Valenciennes Unit, FRANCE, Alstom De Dietrich, France, DUEWAG , GERMANY, Bombardier Transportation, GERMANY, Instituto Superior Técnico, PORTUGAL, , LAMIH – UVHC , FRANCE, Cranfield Impact Centre, UNITED KINGDOM, FMH - Laboratório de Ergonomia, PORTUGAL, ANSALDOBREDA S.p.a., ITALY, Alcan Alesa Engineering Ltd., SWITZERLAND, MIRA Ltd, UNITED KINGDOM, Régie Autonome des Transports Parisiens, France, Technische Universitaet Berlin, GERMANY, Berliner Verkehrsbetriebe, GERMANY.

The support of Mr. Joost de Bock, European Commission, Directorate-General XII, is greatly acknowledged.

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