Megastructures: Built from Disaster: Trains

Thursday 8th October 8.00pm

Continuing this week is the documentary series that explores how disasters throughout the world have influenced the evolution of modern engineering. This instalment examines how a series of high-speed rail crashes forced engineers to incorporate a number of safety features into their designs for the trains of the future.

High-speed trains are an essential part of modern travel, slashing journey times between cities and transporting passengers in comfort and style. But with the need for speed comes a greater necessity for safety. When fast trains crash, the results can be catastrophic. Collisions throughout history have exposed flaws in safety technology and rail infrastructure – flaws that the designers of new trains are striving to eradicate.For French engineer François Lacôte, the man behind the revolutionary new AGV train, learning from past mistakes is an essential part of designing for the future. “We take into account all the events, incidents and accidents so that our new ideas can benefit from this experience,” he says. “We are constantly learning.”

The world’s worst ever high-speed rail crash took place on 3 June 1998 in Eschede, Germany. With 287 passengers on board, ICE train 884 was travelling at 200km/h from Hanover to Hamburg when it derailed and hit a road bridge. The impact caused the bridge to collapse on top of the crumpled carriages, trapping hundreds of passengers inside. The accident killed 101 people.

Investigators discovered that a wheel failure caused the Eschede crash. To reduce vibration, ICE trains used rubber-cushioned wheels in favour of solid ‘monoblock’ wheels. The steel frame of one of these wheels fractured and caught on a set of points, forcing the carriages off the rails. Since 1998, all points on the German network have been moved away from bridges, while rubber-cushioned wheels have been replaced with monoblocks.

Designers working on the AGV have taken structural steps to ensure that the aluminium shell and the steel under-frame remain intact in the event of a crash, while the undercarriages – known as bogies – are located between the cars to prevent jackknifing. The AGV bogies also feature their own motors, eliminating the need for locomotives at either end. “The motors are distributed along the train, giving us a low centre of gravity,” says Lacôte.

On 27 June 1988, a runaway train careered into Paris’s Gare de Lyon station and ploughed into a stationary train. Eyewitness Dominique Pavy missed the incident by seconds, having left the stationary train just seconds before impact. “I saw things for which I have no words to explain,” she recalls. The cause of the crash, which claimed 59 lives, was the failure of the air braking system. The control centre then locked down the system using a ‘general closure procedure’, little realising that this overrode an automatic safety feature that would have directed the runaway train into an empty platform.

To avoid the failure of air breaks, Lacôte has done away with them altogether in the AGV. Instead, he employs a system called ‘dynamic braking’, whereby the magnetic field powering the motors is reversed. In the AGV, the energy created by this braking system is then turned into electricity and sold back to the national grid. “We actually make money every time we brake this train!” says Lacôte. To prevent the carriages collapsing as they did in Gare de Lyon, the nose of the AGV features a revolutionary threephased shock absorber designed by Thierry Yonnet.

To keep up with developments in train technology, it is essential that the rail infrastructure is also modernised. European engineers are now working on a fully automated train control system, which will put an end to train signals and eliminate a major cause of delays and accidents in the past. Using a satellite radio communication system, information from the control centre can be transferred directly into a train’s on-board computer, such that drivers may no longer be necessary. “Once [the system] is introduced throughout Europe, it will be the end of an era,” says railway expert Christian Wolmar. “Essentially trains will be controlled from outside rather than in the cab.”

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