Changes to train times

 

Buckled Rail

How buckled rails, and the risk of buckled rails, lead to delays - and what the industry is doing to reduce them

 

On warm 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 are subject to strong compression. This expansion has to be managed to reduce the risk of track buckling.

If the track does buckle, the line must be closed and the track repaired before services can resume, causing considerable disruption. Usually, these repairs can't be done until the temperature of the rails has dropped.

If a section of track is judged to be at risk, local speed restrictions are introduced - slower trains exert lower forces on the track and reduce the chance of buckling.

How the industry prevent rails buckling

  • If the track comprises short rails bolted together, small gaps are left between each length to allow for some expansion
  • Most track is made up of long stretches of rail that are stretched and welded together, resulting in reduced compression - and a much lower risk of buckling - when they heat up
  • The stability of the track is checked each winter and any weaknesses are strengthened before the summer arrives; typically this includes replenishing the ballast that surrounds the sleepers, and re-tensing continuously welded rails
  • Paint "at-risk" rails white so they absorb less heat, reducing rail temperatures. Typically a painted rail will be five to ten degrees centigrade cooler than an unpainted rail
  • Continually enhancing measures for calculating rail temperatures, including installing probes that give instant alerts when track temperatures rise
  • On very hot days when high rail temperatures are widespread, speed restrictions are imposed at vulnerable locations; slower trains exert lower forces on the track, reducing the risk of buckling
  • In some parts of Britain’s rail network, tracks are laid on reinforced concrete slabs rather than on sleepers and ballast (the bed of stones that supports the sleepers), helping to prevent rails from buckling

Last updated:   13 January 2017