Why is my train stopped at a red signal?

The short answer#

A red signal means the stretch of line ahead is not yet clear for your train. Usually another train is still in it, or another train is crossing your path at a junction. The signalling stops your train automatically until the way is clear, and most holds like this are short.

Less often, the signal is red because something has failed. The railway is designed so that a fault turns signals red rather than green, which is safe but can mean a longer wait.

What a red signal means#

Main lines in Britain are divided into sections, and the signalling allows only one train into a section at a time. The signal at the start of each section tells the driver whether it is safe to enter. Network Rail describes what the colours tell the driver on a four-aspect signal:

• Red: the next section has a train in it. Stop.
• Single yellow: the next section is clear, but there is a train in the one after it, so expect the next signal to be red.
• Double yellow: the next two sections are clear, but there is a train in the one beyond.
• Green: the line ahead is clear.

The signalling knows where trains are from equipment in the track: track circuits that detect a train on a stretch of rail, or axle counters that count wheels in and out of a section. That is why a driver often slows down before you ever see a red signal: the yellows ahead of it are the warning.

A red signal also has a safety margin beyond it, usually 183 metres of clear track, in case a train stops slightly late.

Why the signal is red#

• A train ahead is still in the section. The most common reason. Your train has caught up with the one in front, often because that train is running late.
• Another train is crossing your path. At a junction the signals are interlocked with the points, so your train waits while another train’s route across the junction is in use.
• The signaller has given another train priority. When two trains want the same stretch of line, signallers decide which goes first. Network Rail’s own definition is that signallers can regulate the service by giving priority to one train over another.
• Something has failed. When the signalling detects a problem (a track circuit fault, points that will not move or lock, a faulty signal), the signals protecting it turn red automatically and trains stop short of it. This is how the system is designed to fail: safe, but slow.

Speed restrictions, for example on very hot days or after engineering work, slow trains down, and a slow train ahead can hold up the trains behind it.

What happens while you wait#

The driver is in radio contact with the signaller throughout. The railway’s Rule Book (module S4) tells drivers what to do when they are held at a signal at danger:

“When your train is detained on a running line at a signal at danger, or without a movement authority (MA), you must contact the signaller as soon as possible.”

A driver may wait up to two minutes before calling if the reason is obvious, which the Rule Book gives as “the section ahead being occupied by a train” or “a conflicting movement being made”. If the signaller says to wait, the driver calls again every five minutes unless told otherwise. The signaller must tell the driver the reason for the delay.

If a signal cannot be cleared because of a fault, the signaller can authorise the driver to pass it at danger and continue at low speed with extra care.

Why a small problem spreads#

Network Rail says that at peak times critical parts of the network run at close to 100 per cent capacity. With no spare room to absorb a delay, one late train holds up the trains behind it, and those hold up the trains behind them. The industry calls this knock-on, or reactionary, delay. Network Rail gives the example that even a blown fuse on a busy route can cause knock-on delays lasting for hours.

So the train holding you up may itself be late because of something that happened miles away, earlier in the day.

If it makes you late#

Your rights come from the National Rail Conditions of Travel (the version in force from 30 July 2026). In plain terms:

• Missed connection. If a delay makes you miss a connection on a ticket for specific trains, Condition 9.4 says you “will be able to travel on the next train service provided by the Train Company(s) with which your ticket was valid without penalty”.
• Ticket running out. If your ticket expires during your journey because your train was delayed, Condition 11.2 says you can still complete that journey without penalty.
• Can’t finish the journey. If disruption stops you completing your journey, Condition 28.2 says a train company will, where it reasonably can, provide another way to your destination, or overnight accommodation if necessary.
• Compensation. Delay is measured at your destination, against the timetable on the day you travel. Every train company pays compensation for a delay of 60 minutes or more, whatever the cause (Condition 32.1). Most run Delay Repay, which can pay from 30 minutes, or from 15 minutes with some companies. Claims must be made within 28 days of your journey (Condition 33.1).

How RailPilot tells you#

Network Rail publishes open data from its train describers, which track each train from one signal section to the next. RailPilot reads it live. When your train is held, RailPilot can tell you that you are stopped at a signal and for how long, which train is ahead of you and why that train is late, where it leaves your route, and how long holds like this usually last, learned from the holds it has seen before. When the way clears, it tells you that too.

This works where Network Rail publishes signalling data for the line you are on. It is not available for the Elizabeth line through central London or the Underground.

Try RailPilot: it is free, with no account, and finds the train you are on from your location. How it works.

Sources#

• Network Rail, Safety Central jargon buster: signal aspects, block sections, axle counters, regulation.
• Network Rail, Track circuits explained and Signals explained.
• Network Rail, Signals and points failures, Speed restrictions and Knock-on delays.
• Office of Rail and Road, Signals passed at danger: the overlap beyond a signal.
• RSSB, Rule Book module S4 (Issue 5, in force at the date above): drivers held at a signal at danger.
• Rail Accident Investigation Branch, Safety digest 03/2019: a driver authorised to pass a signal at danger.
• National Rail, Conditions of Travel, from 30 July 2026: Conditions 9.4, 11.2, 28.2, 32.1 and 33.1.
• Office of Rail and Road, Delay compensation claims factsheet: Delay Repay 15 and 30, and which companies run which.