How problems with signals and points cause delays – and what we’re doing to prevent them
How we’re reducing signalling failures
Signals can fail for different reasons, such as a power cut or blown fuse in the circuit. Our signalling system is designed to ‘fail safe’, to prioritise safety.
To avoid interruptions in the power supply, here are just some of the measures we are taking.
- We’re introducing uninterruptable power supplies (UPS), which take over when the main power supply is cut, minimising delays to passengers. We most recently introduced them on the West Coast and will continue to do so as part of ongoing resignalling schemes.
- In areas that don’t have UPS, we’re making the power supply more reliable by replacing ageing cable.
- We continually monitor the health of our power supply system using wireless monitoring backed up with annual inspections.
- We’ve also invested in fault-finding equipment so we can fix problems before they happen to avoid delays.
- Our intelligent technology lets us remotely monitor the condition of signalling systems and identify faults as soon as they happen. This means we can respond more quickly so trains can run again sooner.
A fail-safe system
Our network is designed so that if something stops working, such as a signal or a set of points, trains will stop before they reach it. So if there’s a power failure, the signal goes black and the driver knows not to pass a signal unless it has a green or yellow light; and if a point fails, the last signal before the set of points affected will automatically turn red so no trains pass.
How we’re preventing delays by increasing the reliability of points
Points are movable sections of track, allowing trains to move from one line to another. On some of our busiest lines, over 100 trains will pass over just one set of points every day.
Like signals, points can fail. They might get clogged with debris or ice, the drive mechanism might fail or, in hot weather, they might expand too much. When points do fail, the system goes into ‘fail safe’ mode.
- Because most points are monitored remotely, we can usually fix the problem before points fail.
- We’ve fitted electric heaters and NASA-grade insulation to points to stop ice forming because this can jam the mechanism.
- We’ve added protective covers to 4,000 points and 2,500 point motors to keep snow out and prevent damage from ice that can fall from passing trains.
- We paint rails white at critical points so they absorb less heat, which reduces expansion. Typically, a rail painted white is 5°C to 10°C cooler than one left unpainted.
- If points do fail, we can often secure them in one position so trains can pass over. This keeps lines open and trains moving.
- When the problem is more serious, we re-route trains to minimise disruption.