Millions of leaves fall onto rail tracks every year. The weight of trains as they pass over the leaves compacts them to form a smooth slippery Teflon like layer, stuck to the track. This layer reduces the grip between the train wheels and track – much like black ice on the roads, making it difficult for trains to accelerate and brake safely. Damp conditions, such as light rain or dew further add to the problem.

The stopping distance of a train is mainly determined by the friction between the wheel and the rail (adhesion), therefore the presence of a slippery contaminant results in increased stopping distances.

To accommodate this, the rail industry implements speed limits in the autumn season to ensure that trains can safely stop, this however results in a reduction of services and the implementation of the “Autumn timetable”

Currently Network Rail operate a fleet of 61 specialist High Pressure Water Jetting trains with jets so powerful they can cut through steel, this extreme pressure requires 130 million litres (or 52 Olympic swimming pools) of water annually. This alone is not sufficient as 80 crews also conduct manual treatment in localised areas.