NGE 220 Unreliable track-circuit operation

Purpose

To prescribe the rules for identifying and responding to unreliable track-circuit operation in the Network.

Identifying unreliable track‑circuits

Reporting

Qualified Workers must report track-circuits suspected of being faulty to the Signaller.

The Signaller must treat the operation of the reported track-circuits as unreliable.

Intervals between train movements

Signallers must treat the operation of track-circuits that have not been travelled over by rail traffic for 72-hours or more as unreliable.

Responding to unreliable track‑circuits

Rail traffic detection failure

Track-circuit operation must be treated as failed and in an unsafe condition if it fails to provide an indication when a train, or a track vehicle listed in the Train Operating Conditions (TOC) manual as operating track-circuits, is on the track-circuit.

Signallers who become aware that track-circuit detection of rail traffic might have failed must:

• set controlled signals allowing entry to the affected blocks at STOP and apply blocking facilities, and
• arrange for the Signals Maintenance Representative to be told about the unreliable track-circuits, and
• make sure that signalling equipment affected by unreliable track-circuits is not used before it is tested and certified as working correctly by the Signals Maintenance Representative, and
• tell the Network Controller, and
• block work rail traffic.

False detection of rail traffic

Track-circuit detection is treated as false if it indicates that the track-circuit is occupied without rail traffic being present.

Signallers who become aware that track-circuits are providing a false indication of the presence of rail traffic must arrange for the Signals Maintenance Representative to certify the track-circuits as working correctly.

Until the track-circuits have been certified as working correctly, rail traffic must be worked in accordance with:

• NSY 512 Manual block working, or
• NSG 608 Passing signals at STOP.