Technology: Can cars make trains safer

Technology 4 June 1994

Many deaths in rail crashes could be prevented if techniques now used
to make cars safer were also applied to trains, according to investigations
carried out at the Motor Industry Research Association.

After the Clapham train crash of November 1988, in which 35 people died
after a commuter train ran into the back of a stationary one at about 56
kilometres per hour, the British Rail subsidiary Engineering Link commissioned
MIRA, which is based in Nuneaton, to study ways of cushioning rail passengers
in a crash. Last week Andy Piper, a researcher at MIRA, told a conference
on railway technology at Birmingham that many of the methods used to reduce
the severity of car accidents could also be applied to trains.

Piper says that the major difference between car and train crashes
is that rail passengers face relatively low accelerations in a crash. In
MIRA tests, a crash involving a sports car produced decelerations on dummies
of 50 g (490 metres per second per second), lasting about 70 milliseconds.
But on a train the impact is softened as the carriages crumple, and a typical
railway crash produces decelerations of about 5 g for approximately 200

In cars, seat belts and air bags are necessary if drivers and passengers
are to have a reasonable degree of protection, Piper says. However, because
of the relatively gentle deceleration on passengers in a train crash, quite
minor changes to the design of carriages could give protection comparable
to that conferred by a seat belt in a car.


One of the easiest ways to protect passengers on a train is to have
all the seats facing backwards, so that in the event of a head-on crash
the seat back restrains passengers. But this is hard to achieve because
most trains reverse at the end of their journey, and in any case passengers
often want to sit facing each other at a table while they have a meal or
a drink. In a head-on crash, the forward-facing passengers hit the hard
edge of the table abdomen-first, and as it digs in it may cause internal
injuries such as a ruptured spleen.

Piper says that the solution to this problem is, in part, to redesign
the leading edge of the table so that it crumples in a crash and softens
the blow. The other part of the solution is to arrest the forward motion
of passengers’ bodies with a ‘knee bolster’ under the table.

Knee bolsters are used extensively in cars in the US, where some states
do not have compulsory seat-belt laws and air bags are the main source of
protection in an accident. Knee bolsters, used in conjunction with air bags,
can then absorb nearly a third of the crash energy. In railway carriages,
the knee bolsters would be placed quite close to passengers’ knees so as
to absorb the energy from the crash as gradually as possible.

Piper says that automotive technology can even help to protect the train
driver, who is the most vulnerable person in a crash. An air bag, much larger
than those used in cars would help to restrain the driver. In conjunction
with an energy-absorbing front end, which would be designed to maintain
a space one metre wide in a collision, this could improve drivers’ safety
in quite serious crashes.

Piper acknowledges though that any design used in trains not only has
to soften the impact in a crash, but also be tough enough to resist the
attentions of vandals.

The next stage of MIRA’s research will be a full-scale test crash. This
will yield data to validate its calculations, and to produce designs for
safety features.