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Friday 25 May 2018

Scotland’s railway prepares for soaring temperatures

Region & Route:

Scotland’s Railway: Scotland

With the country expected to enjoy one of the hottest May bank holidays on record this weekend, special preparations are being made to help keep Scotland’s railway on the move.

During heatwaves, rails in direct sunshine can be as much as 20°C hotter than air temperature and expand as they get warmer – sometimes causing them to curve or buckle.

Network Rail engineers will be carrying out additional track inspections over the weekend and deploying special remote monitoring equipment to help spot rails which are becoming too hot.

If rail temperatures in an area do rise significantly, some localised speed restrictions may be put in place to slow trains down and reduce the amount of force being placed on the rails.

Engineers have also been preparing in advance – stressing sections of track (artificially stretching the rails) in known hot-spot areas and also painting rails white to help reflect the sun and keep them up to 10°C cooler.

David Dickson, ScotRail Alliance infrastructure director, said: “On very sunny days, rails in direct sunshine can be as much as 20 degrees centigrade above air temperature.

“As rails are made out of steel, they expand as they heat up and can buckle, causing disruption to travel.

“If a section of track is judged to be at risk, we introduce speed restrictions – slower trains exert lower forces on the track and reduce the chance of it buckling.

“Our engineers will be out throughout the weekend, monitoring rail temperatures and working hard to make sure we effectively manage any potential issues and keep customers on the move.”

How we prevent tracks from getting too hot:

We work closely with specialist weather forecasters and local weather stations to make plans and take action so rails are less likely to buckle.

• Our teams check track stability each winter as part of ongoing maintenance, and strengthen any weak parts before summer.
• We paint certain parts of the rail white so they absorb less heat – and expand less. Typically, a rail painted white is 5°C to 10°C cooler than one left unpainted.
• As most track is made up of long pieces of rail that are stretched and welded together, there is much less chance of buckling in very high temperatures because there is reduced compression.
• When a track is made up from short rails bolted together, we leave small gaps between each one so that expansion doesn’t cause a problem.
• We’re always improving how we measure and calculate rail temperatures. One way we’re doing this is by installing probes that alert us when track temperatures rise to give us chance to take action and stop a problem before it happens.
• In some parts of the network, tracks are laid on reinforced concrete slabs rather than on sleepers and ballast (the bed of stones that supports the sleepers). This helps to prevent rails from buckling.