Network Rail helps to keep the railway running as temperatures soar.(Network Rail)

Temperatures across Britain have been reaching highs of 33.5°C on the country’s hottest days of the year so far (Tuesday 19 July and Wednesday 20 July), and Network Rail is working together with the rail industry to ensure services run for passengers despite the potential disruption that hot weather can cause.

Cabling renewal at Shenfield

Upgrades to overhead cabling on the Great Eastern Main Line are reducing heat-related delays .(Network Rail Image)

Regular updates from forecaster MetDesk before 03:00 every morning keep the Network Rail Weather Service within the National Operations Centre (Network Rail’s operational readiness hub) informed of any severe or unusual weather. They forecast the weather conditions for that day and the four following days so Network Rail teams across the country can plan in advance.

Weather stations across the Routes – the eight geographical areas of the rail network – help to provide accurate forecasts locally.

When severe weather is forecast, route-based groups (called Extreme Weather Action Teleconferences, or EWATs) get together to plan and prepare – and a number of these have been held over the past few days to get ready for the hot weather.

In response, teams of Network Rail engineers have been on call ready to deal with any issues. Temperature probes have been used to measure rail temperatures, and speed restrictions applied where needed to minimise the risk of the track buckling.

Year-round preparation

Network Rail manages the railway and carries out improvements throughout the year so trains can run in all weathers.

The rails are painted white at critical points such as junctions so they absorb less heat, reducing expansion. Typically a painted rail is five to ten degrees cooler than an unpainted rail.

Most track is made up of lengths of rail that are stretched and welded together for reduced compression – and a lower risk of buckling – when they heat up. Where there are short rails bolted together instead, Network Rail leaves small gaps between each length to allow for some expansion.

Where possible, Network Rail plans to avoid carrying out work that will disturb the stability of the track during the summer, as it increases the chance of buckled rail.

Track stability is checked before the arrival of summer. Typically the ballast – the stones beneath the track – is topped up, and the long welded rails are re-tensed (stretched) to ensure stability.

Weather is also considered during long-term improvement works, such as the renewal of the overhead cabling, which helps to power electric trains, on the Great Eastern Main Line. High temperatures can cause overhead cables to sag and lead to speed restrictions on train services, but the new upgrades – replacing existing cabling with auto-tensioned overhead line equipment that doesn’t go slack in the heat – will lead to better train performance and more reliable journeys.

Forecasting rail temperature

Most of the network is resilient to track temperatures of 46°C – roughly equivalent to air temperature of around 30°C – but rails have been recorded at higher temperatures than this over the past few days.

A special Hot Running Rail Forecast tool on the Network Rail Weather Service website indicates the maximum temperature rails will reach and how long they will be over 46°C, based on solar radiation. On Tuesday (19 July) the hottest track temperatures forecast were at 51°C.

The tool is just a guide, but accurate, with the Wessex route – which runs from London Waterloo station to parts of the south and west of England – measuring the 50°C that it predicted when using their temperature probes on the rail.

At rail temperatures of 54°C or hotter, a 90mph speed restriction for passenger services is necessary between 12:00 and 20:00, and a 60mph restriction is required between 14:00 and 18:00 at 58°C.

The speed restrictions for trains are in place to ensure services can continue to run, although at a slower speed, by helping to prevent buckled rail – a potential problem on very warm days that can cause serious disruption to train services.


Buckled rails

If the rail buckles as a result of the steel rail heating up and expanding, it can cause serious travel disruption. The line has to be closed and the track repaired before services can continue. Usually such repairs can only be done when the rail temperature has dropped, meaning it can take time for the line to reopen.

This is why Network Rail introduces speed restrictions if a section of track is judged to be at risk – slower trains exert lower forces on the track and reduce the chance of buckling.