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Therefore, rail traffic is affected by leaves on the tracks

By on October 11, 2019
Photo: Gustav Kaiser

What can some leaves on the tracks do? Pretty much, if you ask the drivers of SL’s rail traffic, especially on the Green Line. Despite demands to keep the timetable, they must slow down if the train is at risk of slipping when braking at the station.

When autumn comes and the leaves fall, many SL travelers are frustrated by the phenomenon of track slippage, that the train slows down because leaves have settled on the tracks. They are not alone. For drivers it is frustrating. They know that the travelers will be delayed, but must put safety first in all situations.

This is how Fredrik Cavalli-Björkman, traffic director at SL, explains what leaf slipping really is:

– The damp leaves stick to the tracks. When train after train passes, the leaves are mashed down to a mass, slippery like soap. This means that the driver must slow down – to prevent the train from slipping when braking.

Especially on the subway’s green line is a problem, as it has the most outdoor stations and many slopes. The slopes are there because the system is built so as to recover energy and tear less on the brakes. The trains are pushed out of the station and are slowed down when they enter the stations – an ingenious idea for the environment but which, just in case of leaves slipping, the trains can have a little extra difficulty in acceleration or braking.

– Of course, we do what we can to prepare, for example the subway tracks for the fall: We remove trees, bushes and shrubs from the area around the tracks to avoid branches and leaves falling on the rails. Dirt, such as exhaust particles and oil, is washed away to prevent the leaves from sticking to the rails. All this happens at night, so as not to disturb traffic, says Fredrik Cavalli-Björkman.

In order to read the weather conditions and adjust the metro traffic there are also three weather stations along the tracks. They collect facts about air and rail temperature, humidity and falling leaves.

Facts – This is what SL does to reduce the problem of leaf slipping:

  • Trees, bushes and shrubs are removed from the area around the tracks.
  • Dirt and oil are washed away so that leaves do not stick to the rails.
  • Facts about air and rail temperature, humidity and falling leaves are collected, so that traffic can be adjusted to weather conditions.
  • Preparedness is increased for the maintenance of the trains.

Facts – This is leaf slipping:

  • Slipping due to leaves and moisture in the air poses problems for parts of rail traffic.
  • If the wheels slip on the tracks during braking and starting, it can cause damage to the wheels and rails.
  • When leaves that have fallen on the tracks are repeatedly run over by the heavy wagons, the leaves are ground down and become like a pulp when mixed with water or moisture.
  • The tracks get really slippery and the braking distance longer, so drivers have to drive slower for safety reasons. It sometimes creates delays.
  • Also wet, such as drizzle, is a problem. At temperatures between zero and five degrees, the water’s ability to drain changes as the water droplets become more viscous.
  • The subway is most affected by track slippage because many stations are located so that braking and acceleration at take-off are done on slopes.
  • Most affected are Green Line, that has the most stations outdoors.
  • Saltsjöbanan and Roslagsbanan are also affected by slippery tracks, while tram and commuter train traffic is less common with slippery tracks.

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Source SL