A fault with the signalling system between Burgess Hill and Three Bridges means trains have to run at reduced speed on the line towards London.

As result, trains running between Burgess Hill and Gatwick Airport may be delayed by up to 20 minutes or revised.

Disruption is expected until 08:00.

Customer advice:

Trains that run between Wivelsfield and Haywards Heath are subject to delays of up to 20 minutes.

You will not need to use an alternative route, but your journey time will be extended.

Trains have been altered to keep running trains on time;

• Services which usually run between Littlehampton and London Bridge are suspended
• Gatwick Express services which usually run between Brighton and London Victoria will now run between Gatwick Airport and London Victoria ONLY

To help you complete your journey, your ticket will be accepted on Southern and Thameslink services via any reasonable route.

Some late running trains may terminate and restart earlier later on in their journeys meaning you could need to change trains more then usual to complete your journey - please listen to station and onboard announcements.

It is advised that you leave extra time to complete your journey, and check your train before you leave to travel.

Planning your journey:

Live departure boards can be found here..

You can view a live map of the network here, and you can also see an alternative route guide here.

Can you tell me more about the incident?

A track circuit failure is disrupting trains which travel from Burgess Hill towards London.

This part of the network uses track circuits to detect the position of trains. These are electrical systems which monitor whether a train is on a section of track. They operate as part of the signalling system, which is designed to be "fail safe".

When a track circuit fails, the signalling system will interpret this as a train remaining in place, even though there may not be a train present at all, or the previous service may have long since left the area.

As a result, further trains cannot be automatically allowed onto the relevant section of track. Train drivers will be stopped by red signals on approach. They will then get verbal permission from the signaller so that they can proceed, and will run at a heavily-reduced speed as far as the next signal. This is so that the drivers will stop safely if they see anything ahead of them.

In some areas, the sections between signals can be several miles long, so this can result in delays building up. Even with shorter sections of track affected, there would still be a delay of at least a few minutes to each journey.

Track circuit faults can be caused by a number of different issues, including electronic faults or obstructions on the track. Network Rail manage the signalling system, including track circuits, and their staff will be investigating as quickly as possible.

Check before you travel:

You can check your journey using the National Rail Enquiries real-time Journey Planner.

Compensation:

You may be entitled to compensation if you experience a delay in completing your journey today. Please keep your train ticket and make a note of your journey, as both will be required to support any claim.