Moving trains create a vortex that sucks in fallen leaves and deposits them on the rails (see Figure 1). During damp or rainy periods, which are frequent in autumn, the coefficient of friction can be reduced to near zero. As the leaf layer dries and hardens on top of the rail it acts as an insulator and interferes with track circuits, sometimes making trains "invisible."

Since passenger (and most freight) trains in the UK have adopted disk braking systems, which have significantly greater stopping power than cast iron brake shoe systems, trains sustain higher speeds before braking for signals or stations. This allows for tighter overall scheduling, which is negatively impacted when adhesion levels and stopping ability are compromised by leaves on the rails.

Railways in the UK have instituted programs to make drivers (engineers) aware of potential problems as the low-adhesion season approaches. New drivers are trained through simulations to recognize low-adhesion conditions and to operate accordingly. Vegetation management is another key component of dealing with seasonal adhesion issues. Since it is impossible to prevent leaves from falling on the track, several technologies have been developed to deal with them.