Leaf-fall risk predictions

During autumn, leaf fall can contaminate the rail-heads across your network increasing the risk of low adhesion. The volume of leaves falling and potentially causing contamination can vary significantly day-to-day, depending on the weather and the behaviour of different trees.

High winds, storms and frosts accelerate leaf-fall with the greatest risk occurring mid-season, when most leaves fall from the trees. The ADAS/Met Office leaf-fall risk (LFR) prediction service warns of leaf-fall contamination up to five days ahead.

Our predictions are used to inform mitigation strategies, reducing the likelihood of safety breaches (e.g. Category A SPADS, station overruns and wrong-side track circuit failures) as well as delays.

The service

ADAS and the Met Office have developed a leaf-fall prediction model that takes into account forecast wind speeds, the volume of leaves remaining on the trees, accumulated leaf litter on the ground and the behaviour of different types of trees. The model also accounts for the effect of frosts and storms on leaf-fall rates.

Our model is unique because it:

• is driven by the most up to date weather forecast from the Met Office;
• draws from a network of tree experts who act as leaf-fall observers and monitor the status of leaf-fall for different tree species;
• guides users on the weather and leaf-fall over the next few days.

Each autumn the service provides:

• daily colour-coded LFR indices for up to five days ahead;
• a 'wind throw index', warning of the risk of fallen debris, branches or trees; 
• the amount of leaf-fall that has taken place throughout the season, indicating its progression; 
• Three-hourly summaries for the London area, providing details of major leaf-fall or wind events coinciding with peak travel times; 
• text summaries of the latest leaf-fall predictions.

Working together

Available since 1995, the LFR prediction service is delivered by the Met Office Rural Environment Team - a group of Met Office experts based at ADAS - who bring together the best in meteorology and ecology. ADAS is a leading land-based research consultancy
with over 40 years experience.