SL is testing white-painted rails to prevent heat-related disturbances

High temperatures can lead to heat-related disturbances such as sun curves and track shifts. Sun curves occur when the rails are exposed to high heat and the track can no longer withstand the extreme compressive forces. Then the track expands, deforms laterally and forms curves. The curves are a serious safety flaw that can cause delays and in the worst case they can lead to derailment.

This summer, SL has tried to prevent such problems – by painting the rails white.

"The purpose is to reduce the temperature in the rails during the hottest hours of the day to reduce the risk of heat-related disturbances," states SL's press communicator Natalie Nordenswan in an email.

Since 2008, the Swedish Transport Administration has mapped solar curves around the country. The authority has identified around 1,000 solar curves in total. During the extreme heat of 2018, a total of 198 sun curves were observed.

By painting the tracks white, the heat is reflected instead of being absorbed. As a result, the heat of the tracks can drop a few degrees, according to SL.

"The traffic administration is evaluating various methods to reduce the risk of heat-related disturbances, by keeping the rails cooler the risk of sun curves occurring is reduced."

The white-painted tracks were already tested in 2019 on the Roslagsbanan railway in northern Stockholm, and this year they continue to be tested in Alvik. The method is also used on certain particularly vulnerable railway sections in warm parts of Europe. The white painted tracks are found in Italy, England and Spain.