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AEA Technology, which operates the former British Rail research centre in
Derby, has developed a system that lets passenger trains continuously check the
state of the railway track (WO 0070148). To compute rail undulations, a
tachometer monitors wheel speed while accelerometers on the sprung wheel mounts
under the carriage check vertical and lateral motion. The information from both
is combined with GPS readings and transmitted to a base station, allowing train
operators to 鈥渕easure rail quality daily, improve safety and decrease the risk
of derailment鈥�.