Track Circuit Failure

How track circuit problems can cause delays - and what the industry is doing to reduce them

The rail network is divided into sections with each forming a separate electric circuit which provides a vital function: they allow signallers to “see” where the train is.

They use this to make sure trains keep a safe distance apart. When a track circuit fails the trains are stopped until alternative signalling arrangements are introduced or the problem is fixed.

Track circuits can fail for many reasons, from flood water causing a short circuit to a layer of crushed leaves insulating the wheels from the track, preventing the axle from completing the circuit, effectively making the train invisible to the signaller.

How the industry is reducing delays caused by track circuit failures

• Investing heavily in remote monitoring of the condition of track circuits so intervention occurs before a failure
• An extensive programme of maintenance and renewal of older and less reliable track circuits
• Upgrading the insulated joints between track circuits to a new type that can be welded into the track
• Introducing a new signalling system, ERTMS, which uses in-cab displays instead of fixed signals along the track
• When a track circuit fails, sometimes services can be kept running by signalling trains manually, but speed restrictions may be imposed to do this