Scientists find out why leaves on the track causes travel chaos

[John Ashworth]

Scientists find out why leaves on the track causes travel chaos

Leaves on the line are a notorious headache for commuters and train companies alike, causing costly delays. Now scientists say they have unpicked why fallen foliage makes rails so slippery.

When leaves are crushed against the tracks, they form a black layer that drastically reduces friction between train wheels and the rails – a situation Network Rail has described as “the black ice of the railway”. But the make up of this slippery layer has been something of a puzzle.

Now researchers say they have revealed a key ingredient: large molecules found in plants called tannins.

“They are the chemicals that make wine dry, and they are present in tea,” said Dr Michael Watson of the University of Sheffield, a co-author of the new research.

The team say the study suggests leaf tannins grab onto iron that has been dissolved from the rails by acids in the foliage, forming a layer of black material that reduces friction between steel surfaces...