How might the heatwave affect Greater Anglia trains?

Published on: Thursday, 14 July 2022
Last updated: Tuesday, 8 August 2023

  • Behind the Scenes

Thanks to Network Rail’s preparations and the continued roll out of our fleet of new trains which all have air con on board, we are in a better position to cope with hot weather than in previous years.

However, the predicted heatwave could still have an impact on train services if anticipated extreme high temperatures do arrive.

Here’s an explanation of how very hot weather can affect different parts of the railway and how we try to minimise delays and cancellations to services.


Steel rails expand in high temperatures. This can cause them to buckle, which means that journeys may be disrupted while repairs are carried out. Rails which have expanded can also cause a type of signalling problem known as a track circuit failure.

Train tracks

Through a process called stressing, Network Rail engineers prepare rails to resist any expansion at all until the rail temperature goes above 27 degrees, with most of the network being able to run normally until the track is over 48 degrees. Rails in direct sunlight can be as much as 20 degrees hotter than the air temperature.

If the rails were stressed to cope with even higher temperatures, they wouldn’t be safe and reliable in winter, risking broken rails when they contract in cold weather.

Ahead of this summer on Anglia, engineers have re-stressed extra rails in places on the network where they are more vulnerable to buckling.

But when Network Rail assesses that the temperature of the rails is going to exceed what it is designed to cope with, speed restrictions are put in place to help prevent problems. Methods of measuring rail temperatures are improving all the time, with remote digital sensors currently in use on Anglia. Better measurement allows earlier and more effective action to be taken.

Another way of minimising problems during summer is to paint rails in white. This reduces the heat they absorb and means they expand less. Typically, a rail painted white is 5 to 10 degrees cooler than one left unpainted. To prepare for this summer on Anglia, Network Rail has added white paint to dozens more points (movable sections of track that are critical for reliability).

Speed restrictions

Every year we work alongside Network Rail to ensure we are prepared for high temperatures and the challenges it always brings, but sometimes the only option to ensure that we can still operate safely, and keep trains running, is to slow the trains down.

A train going over a hot rail at a slower speed exerts less pressure on the rail and will help to prevent it buckling.

If trains have to run more slowly, it means there will be fewer trains as a result, but this is better than causing a bigger problem and then being unable to run any trains at all.

We are sorry for the impact this has on your journey if it happens.

Ground underneath the track

Prolonged hot and dry weather can cause the ground underneath the railway to shrink, destabilising the tracks. This can mean disruption to services.

Since last summer, Network Rail Anglia teams have dropped 54,000 tonnes of additional ballast and carried out 131 extra shifts with machines called tampers, which move ballast to align the track correctly. This will help to support the rails even when the ground underneath shrinks and changes shape in dry conditions. A new data tool is also being used so that engineers can identify potential risk sites and take appropriate action.

Overhead lines

Overhead lines give power to the trains by conducting electricity through the pantograph on top of the train.

During hot spells they can expand and sag in the heat. This can cause the train’s pantograph to become entangled in the wires which could even pull them down, resulting in delays and cancellations while the complex repairs are carried out.

Network Rail has replaced much of the oldest overhead line equipment with new auto-tensioned systems which can cope better with temperature changes – and we are seeing the benefits of this.

The most recent overhead line upgrades on Anglia were between Forest Gate and Chelmsford and on the Southend Victoria line. These projects to install the latest equipment were completed in 2018 and 2019, improving reliability during the summer months.


Climate change doesn’t just mean higher temperatures. It is also leading to more extreme weather in general, including very heavy summer rainfall that has the potential to cause flooding and affect services.

In the last couple of years, Network Rail has been using an innovative forecasting system for convective rainfall, which tends to be heavier and harder to predict. The technology provides better insight into where and when torrential downpours will happen so that colleagues can consider any changes to the train service. It also helps engineers prepare to remove water from the railway, with pumps put on standby around the region in the days leading up to very heavy rain.

In addition, lots of work has recently been done by Network Rail to create flood plans for high-risk sites and assess the condition of drainage infrastructure. Drainage improvements are continuously being made around the region, for example on the line between Maryland and Forest Gate recently. The Manor Park area has automated pumps which have an in-built messaging system to notify maintenance teams of increased water levels.


Our fleet maintenance teams will be doing everything they can to ensure that the air con on our trains is in working order.

Thanks to the introduction of our new trains, more of our routes will benefit from trains that have really good air conditioning systems this summer.

In total, there are 1,100 air conditioning units on board our new trains, which are now running on every part of our network. We only have a very small number of trains left on our network without air conditioning.

We’ve also switched off the heating on all our trains. On some of our older trains, you may feel warm air blowing through the vents at times on hot days if the train has only just started up – much like how your car blows through hot air from outside until the air con kicks in.

However, if you do board a train that feels uncomfortably warm please report it on twitter to @greateranglia or contact our customer relations department on 0345 6007245 (option 8) or [email protected] and let us know which service you are travelling on and the carriage number if you know it which is usually displayed above the internal carriage door.

If the problem is caused by a fault, we can then arrange for repairs to be carried out, sometimes by using a mobile engineer who can board the train to try and fix the problem whilst it is in service, or by scheduling it to visit a depot overnight.

Stay hydrated

Remember to keep hydrated while travelling. Take a reusable water bottle with you and make use of our free water refill fountains at some stations.

We have free water fountains at 22 stations on our network – Billericay, Bishop’s Stortford, Broxbourne, Cambridge, Cambridge North, Chelmsford, Cheshunt, Colchester, Ely, Great Yarmouth, Harlow Town, Hertford East, Ipswich, Lowestoft, Marks Tey, Norwich, Wickford, Witham, Rochford, Shenfield, Tottenham Hale and Waltham Cross. There are also water fountains at London Liverpool Street.

We will be doing everything we can to get passengers from a to b reliably and in comfort.

Please check before you travel

Where possible, we will try to make you aware in advance of any predicted timetable changes due to hot weather.

Check for travel updates on our homepage and our app.