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Broken Rail

Why rails can break - and what the industry is doing to reduce the incidence and impact of broken rails

The steel rails in railway track are strong and durable - they can safely carry many hundreds of millions of tonnes of traffic over their lifetime.

Small defects may be present in rails from manufacture or installation, or they may be formed as trains pass over. These small defects can grow as more trains pass over and can ultimately cause the rail to break.

Most broken rails occur in winter. In very cold conditions rails can be five degrees below the air temperature, putting the rails under a lot of tension, and they become more vulnerable to breaking at a defect when trains pass over them.

Broken rails also cause a secondary problem: the network is divided into small sections of track which form separate electric circuits. These circuits provide a vital function, allowing signallers to “see” where trains are so they can make sure that all trains remain a safe distance apart. When a rail breaks, the electric circuit is broken - known as a track circuit failure - and trains must be stopped until the problem is solved.  

What the industry is doing to prevent rails breaking and any subsequent delays

  • Small defects are regularly removed from the surface of rails by grinding the surface of them
  • On-track teams and Measurement Trains, which are equipped with ultrasonic and high definition video equipment, check rails for defects
  • Working with rolling stock manufacturers to minimise the damage caused by trains to the rails
  • Replacing bolted joints between rails with welded joints which are stronger and less likely to break
  • In problem areas new rails are installed that are even harder-wearing
  • The more heavily a line is used, the more frequently it is checked for defects
  • When a serious defect is found, immediate speed restrictions are imposed to allow services to continue safely; repairs usually take place overnight
  • If a rail breaks it may be possible to clamp it and allow trains to continue running, subject to speed restrictions, until the rail is replaced
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Last updated:   11 January 2017