Railways. Steel rails expand and tend to buckle in the heat – whatever the climate. According to Network Rail, railways worldwide are designed to operate within a 45C (81F) range, according to the local conditions.
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Just as people can suffer sunburn or heat stroke from too much exposure to sunlight and hot temperatures, rail can bend or warp because of a blistering sun and sweltering temps. If the rail malformations known as a sun kink or track buckle aren't repaired in a timely manner, trains can derail.
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.
Trains run on steel tracks, which respond to changes in temperature. Steel contracts in the cold, which could cause rails to pull apart. It expands in the heat, which can make the track buckle sideways (known as a “sun kink”).
Because rails are made from steel, they expand as they get hotter, and can start to curve this is known as 'buckling'. Most of the network can operate when track temperatures heat up to 46°C – roughly equivalent to air temperature of around 30°C – but rails have been recorded at temperatures as high as 51°C.
Intense heat causes steel railroad tracks to expand and to buckle under the extra stress. Trains reduce their speed in extreme heat to put less additional force on the tracks, resulting in delays.
If it gets hotter than 100 degrees, the rail goes into compression and expansion, causing a potential buckle or kink. Research has shown that a rise in rail temperature of anywhere from 40 to 50 degrees above the RNT can cause a potential buckle.
In hot weather, the overhead lines that provide power to the trains can expand and sag. To avoid damaging the lines, trains must travel more slowly. If the overhead lines are damaged, we have to cancel or divert train services until they are fixed. This causes delays.
We introduce speed restrictions during the hottest part of the day at vulnerable locations as slower trains exert lower forces on the track and reduce the likelihood of buckling. 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.
The horn alerts people that a train is approaching a railroad crossing. It can also be used to warn animals or trespassers in our right-of-way along a section of track. Many people don't realize that federal and state regulations require us to sound the horn whenever we approach any crossing.
In order to cope with the adverse effects caused by thermal expansion and contraction, on the ordinary track line, there will be a special gap between the rails, about 6mm wide, called the expansion joint.