Forschung Aktuell

 Science Service
Nr. 1, September 2000

TU Berlin Science Service of the TU Berlin
Nr. 1 / September 2000

Passenger safety
Improved safety with energy-absorbent couplings

A new interior design for rail vehicles is intended to improve the safety of passengers. And new materials also offer improved crash protection. Scientists at the TU Berlin have developed an energy-absorbent plastic which can be injected into the coupling and buffers between rail-carriages. This is more efficient in absorbing energy than the shock absorbers of a motor vehicle.

If a tram driver has to stand on the brakes, then the passengers may well find themselves jerked off their seats. Although seat-belts, air-bags and ABS braking systems are standard on motor vehicles, little has as yet been undertaken to ensure the safety of passengers in rail vehicles. This is the goal of scientists working on a number of different research projects at the Technische Universität Berlin. In addition to developing active safety systems such as brakes and signals, work is also going on to improve the design of rail vehicles, as a way of improving their passive safety.

Padding, lap-belts and shoulder belts, or improved deformation zones are tested for their effectiveness by means of computer simulations and passenger safety tests. "If we know how the energy can be distributed in the event of a frontal crash" explained researcher Steffen Sohr, "then we can test for suitable materials which are able to soak up the forces involved." The goal is to absorb the deformation energy within a fraction of a second after a collision, and distribute this without harming the passengers.

"For example, we can construct the couplings between carriages so that these absorb energy in the event of a collision and damp the forces involved." Scientists are testing elastomers which have very special properties. If it is put on a surface it will slowly spread out flat. "But if I hit it with my fist, the elastomer absorbs the deformation energy and springs back to its original shape;" explains Steffen Sohr. This elastomer can be filled in the metal buffer sections. Due to the lattice of bonds between the molecules and the electrostatic forces attracting them, "this special buffer absorbs more energy than the shock absorber on a motor vehicle".

Such energy-absorbing systems can significantly improve passenger safety in trams, but are not effective when it comes to protecting passengers in high-speed trains.

"By means of a special computer simulation program, I can try out various seating arrangements and see which is best at softening the effects of collisions on passengers", added Steffen Sohr. In addition to the seating position, the actual seats themselves can have an affect on the outcome of a collision. Thicker upholstery, and spring-mounted foot-rests and back-rests can help to decelerate the passenger gently and reduce the risk of injury.

The results of this research work have already generated interest among manufacturers, as one example in Berlin illustrates: The new series of underground and urban railway carriages being built in Berlin will include the elastomer filled couplings. And politicians specialising in transport have also recently called for seat-belts to be made compulsory in all trains following a tragic rail accident in Brühl, Germany, in which eight passengers were killed and 148 were injured.


Contact: Steffen Sohr and Prof. Markus Hecht, Technical University Berlin, Institute for Road and Rail Traffic
Special field: Rail vehicle technology
Research project: "Passive Safety and Designing Safe Interiors for Rail Vehicles"
Address: Salzufer 17 - 19, 10587 Berlin, Germany, Tel: +49 30 314-22444. E-mail:, Internet:

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