A NEW type of railway safety system could give train drivers a better way to
warn other drivers that the track is blocked, according to a British patent.
At present, drivers have to lay a small explosive charge on the rails, which
is detonated when another train passes over it. In his patent (GB 2347251),
Stevan Cambridge of Darlington calls this practice 鈥渦nreliable鈥� and a 鈥渉ealth
hazard鈥�. One alternative is to place metal clips on the rails to create a short
circuit that makes signals change. But this forces the driver to leave the train
unattended, and dirt on the rails means that sometimes 鈥渃lips have failed to
warn approaching trains of danger鈥�, Cambridge鈥檚 patent says.
Cab radios are fitted in only a 鈥渧ery small鈥� number of trains, Cambridge
notes, and trackside phones are of limited use and are often vandalised. He says
that accidents have also been caused by 鈥渙perator error鈥� in signal boxes.
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Cambridge鈥檚 idea is to use the rails to transmit alarm signals. Surprising as
it seems, examiners at the British Patent Office have found no evidence that
anything similar has been tried before.
The patent says a 鈥渄istress panel鈥� should be installed in the train cab.
Drivers who want to warn other trains that the line is blocked simply flick a
switch on the panel. This powers a transmitter beneath the train, which sends an
electric current through the wheels and into the rails.
The signal sounds an alarm and lights a distress lamp on all other trains on
the track. If a train is derailed, the driver can use an induction loop to
transmit the same distress signal.
Similar devices can be fitted in signal boxes so that signal operators can
send a warning to all trains in the area. Cambridge says his invention could be
linked to automatic train protection systems, which prevent trains passing red
lights in so-called Signal Passed At Danger (SPAD) incidents. It would tell all
trains and signal boxes in the area that a train has tried to pass a danger
signal. A spokeswoman for Britain鈥檚 Health and Safety Executive said last week
that it would like to hear from Cambridge so that it could study his ideas. 鈥淎ll
existing systems are flawed, there is no dispute on that,鈥� she says.
The patent was published as the public inquiry continues into the train crash
last October in Paddington, west London, in which 31 people died. In the crash,
a local train passed a red signal and collided with an oncoming high-speed
train. The inquiry (www.lgri.org.uk) has been dominated by arguments over
the relative merits of different types of train protection systems.
Victims鈥� families want Lord Cullen鈥檚 inquiry to recommend the national use of
the Automatic Train Protection System. ATP continuously monitors a train鈥檚 speed
to make sure it is not going too fast to stop at red lights further up the line.
A much cheaper alternative to ATP is the Train Protection and Warning System.
TPWS does not monitor speed continuously, but does so near to signals using
trackside beacons. Many observers consider this less safe than ATP.