Rail passengers are being warned to only travel if absolutely necessary in the record-breaking hot temperatures forecast for early next week.

The rail industry is especially advising avoiding travel from the middle of the day onwards when the hottest temperatures occur. The warning comes as there are likely to be cancellations and delays on the railways. This isn’t because of a shortage of staff or trains, but because the heat affects the railway itself and that requires trains to run slower to reduce the stress on the tracks, and hence fewer trains can use the railway.

Buckled rails 2018 (c) Network Rail

The long railway tracks expand in the high heat, and while they are designed to expand a bit, the heatwave is far outside the temperature range they are designed to work in. All railways around the world are designed for average temperatures for the region they are built for, but exceptional temperatures can’t be designed out of the railway.

In the UK, the railway is designed for the UK’s average summer air temperature of 27 degrees Celcius. As steel absorbs heat easily, the rail track can however be as much as 20 degrees hotter than the air temperature. While the railway in the UK is designed to cope with track temperatures up to around 45 degrees, next week rail track temperatures could exceed 60 degrees.

In exceptional conditions, a kilometre of railway track can try to expand by as much as half a metre. It’s clamped to prevent such a massive expansion, but that then puts stress on the sleepers and ballast trying to hold the track in place. Even if the track doesn’t buckle, the twisting between sleepers is more likely to cause track circuit failure, and that affects the signals.

It would be possible to instal railways to cope with higher temperatures, and when installing steel rails, Network Rail uses a process called ‘stressing’ to protect against buckling. This sets the range of temperatures the track can comfortably cope with. Stressing rails to cope with higher summer temperatures would however then mean they are less resilient to low temperatures during winter. So it’s a balancing act and generally works, except during the sort of rare heatwave we’re having at the moment.

In the past, tracks included expansion gaps in them, hence the long-lost sound from a train trip of the wheels regularly bumping over the gaps. However, those tracks needed a lot of maintenance and the railways were eventually able to introduce far longer lengths of continuously welded tracks. No gaps, but also no space to expand.

So the regular, expensive and annoying maintenance of short lengths of railway track has been replaced with the fairly rare problem of tracks buckling in heatwaves.

Steel rails absorb heat easily and tend to be around 20 degrees above the surrounding air temperature. Pretty much the only thing that can be done to help is to paint the railway tracks with white paint which can reduce their temperature by 5-10 degrees, but with the current forecast temperatures, that’s still not going to be enough to prevent problems.

Hand painting tracks in key areas (c) Network Rail

The heatwave temperatures will force the railway to bring in the speed restrictions on lines across the country to ensure the safe running of trains as they will be running over tracks that may have distorted in the heat, so they need to run at a slower safer speed.

There can also be problems with overhead power lines sagging in the heat and that also causes trains to slow down due to the unreliability of the electricity connection and the risk of the train’s pantograph getting caught up in the sagging wires.

Network Rail says that its extreme weather action teams (EWATs) are preparing for the heatwave conditions and response staff will be deployed across the nation to mitigate the impact of these extreme conditions where possible, but passengers are likely to experience disruption if current forecasts are realised.

The impact on train services will vary by region, but the rail industry is warning that journeys will take significantly longer and there is a high likelihood of cancellations, delays and last-minute alterations.

Most of the train companies in the southeast of England are issuing amended timetables to help people preplan any changes they might need to make, so you should check with the train company directly for information. Online journey planners will be updated on Sunday for Monday’s travel and on Monday for Tuesday.

However, the following companies have already issued advice:

Chiltern Railways

A severely-reduced timetable will be in operation as follows:

1 train per hour Marylebone – stations to Birmingham Moor Street (and vice-versa).

1 train per hour Marylebone – stations to Oxford (and vice-versa).

1 train per hour Marylebone – stations to Aylesbury (via High Wycombe, and vice-versa).

1 train per hour Aylesbury Vale Parkway – Amersham (and vice-versa).

London Underground Metropolitan Line services should be used between Amersham and stations to Baker Street.

No Chiltern Railways service to/from Stratford Upon Avon.

Greater Anglia

A reduced service will operate on the Norwich-London Liverpool Street and Cambridge-London Liverpool Street main lines and on the Southend-London Liverpool Street route.

A shuttle service will operate on the Harwich-Manningtree, Braintree-Witham, Southminster-Wickford and Clacton/Walton/Colchester Town-Colchester branch lines to a normal frequency, but without direct services to/from London.

A normal timetable is currently planned for regional services between Norwich and Sheringham, Great Yarmouth, Lowestoft and Cambridge/Stansted Airport; between Ipswich and Lowestoft, Felixstowe, Cambridge and Peterborough; and on the Marks Tey-Sudbury line.

The Stansted Express service between Stansted Airport and London is likely to remain half-hourly but journeys will take longer.

Gatwick Express

Will not run but Southern services will run in their place making extra stops.

Great Northern

A train shuttle will run between Cambridge and Kings Lynn, this will mean a change of trains at Cambridge for journeys through to London.

Services between Moorgate and Stevenage/Welwyn Garden City will be reduced with 2 trains per hour on each route.Peterborough / Horsham services will only run between Peterborough and Kings Cross.

There will be no services between Finsbury Park and St Pancras, this means no peak services between Sevenoaks, London and Welwyn Garden City.

Southern Railway

Southern services will also be significantly revised and more detail about the changes that are needed will become available over the weekend.

Southern metro services between East Croydon and London Bridge via New Cross Gate will not run.

Southern metro services between Caterham and London Bridge via Tulse Hill will not run.

South Western Railway

Speed restrictions will particularly affect mainline services, with long-distance services to Exeter, Salisbury, Bournemouth, Weymouth, Southampton and Portsmouth most likely to be impacted. To help customers, SWR is allowing people with tickets for travel on its services on Monday and Tuesday to travel on Wednesday and Thursday instead.


Bedford to London services will be reduced to 2 trains per hour.Luton to Rainham services will run stopping at all stations between Luton and London, and they expect these services won’t be running south of London Bridge.

St Albans to Wimbledon/Sutton services will be suspended throughout.

There will be no peak services Thameslink services to or from Orpington

There will be no Thameslink service between Sutton and London either via Mitcham Jn or Wimbledon

There will be fewer services between London, Gatwick, and Brighton.

Services between Horsham and London are expected to be amended with a change of trains required.

There will be no Thameslink service to/from East Grinstead or Littlehampton

Track temperature sensors (c) Network Rail

This article was published on ianVisits


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