WheelChex is a brand name for a Wheel Impact Load Detector (WILD) system used by
Network Rail.
This line-side equipment measures the impact upon the railhead of each wheel of a passing train (eg, if it has a wheel flat), and provides details of all trains with wheel loads outside acceptable limits.
When an alarm message is generated by WheelChex, Network Rail Operations Control will identify the train involved and notify the signaller at the centre through which the train will shortly pass.
This will enable the train to be stopped at a suitable location for the driver to examine the wheel-sets concerned.
The train can then be taken out of service, or speed restricted to minimse the possibility of derailments or damage to track caused by wheel defects or overloaded vehicles.
The WheelChex at Braidwood made the news on
29th September 2004 when an alarm was generated by
390041 working the first relaunched "
Royal Scot" Glasgow - London Euston at the launch of
Virgin West Coast's accelerated timetable. The train was terminated early at Carlisle.