Why do ‘leaves on the line’ cause train delays, especially in autumn? The serious danger comes from a series of physics challenges: Leaves are sucked onto the tracks by the fast moving trains. The train wheels crush them into a slimy black pulp, releasing leaf oils that lessen friction. Mixed with rain, this super thin lubricant becomes more slippery than soapy water on the tracks.
Related reading: A Leafy Curse – The Physics of Leaves on the Track.