During autumn, leaf fall contamination and low levels of moisture on the rail head increases the risk of low adhesion issues..
Leaf-fall and Low Adhesion risk predictions
During autumn, leaf-fall can contaminate the rail-heads across your network increasing the risk of low adhesion. Small amounts of moisture from drizzle, light rain, dew and fog also exacerbate low adhesion issues on the railway. 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.
Our leaf-fall and low adhesion 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
The Met Office have been delivering leaf-fall services to the rail industry for over 20 years, during which time we have continually researched and developed our adhesion models to improve the predictions available to the rail industry. The leaf-fall prediction model 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 at fine spatial resolutions. The model also accounts for the effect of frosts and storms on leaf-fall rates.
We combine the leaf-fall predictions with a blend of weather models that ascertain the risk of low levels of moisture on the railhead. The skill of the models used in the low adhesion forecasting system captures the transient nature of low adhesion in space and time at fine spatial and temporal resolutions.
We also provide a wind throw warning service, which provides the risk of fallen trees and tree debris, as part of the service.
- Our forecasts are available at hourly resolution out to 48 hours, moving to 3 hourly, 6 hourly and daily for longer lead times.
- Forecasts are available for up to 10 days in advance and we also provide an autumn prospects service for longer term planning.
- Sub hourly rainfall predictions are also available for automated operational decisions.
Our models are unique because they:
- are driven by the most up to date blend of weather data and adhesion forecast models from the Met Office;
- draw from a network of tree experts who act as leaf-fall observers and monitor the status of leaf-fall for different tree species;
- guide users on the weather and leaf-fall over the next few days.
Each autumn the service provides:
- daily colour-coded risk indices for up to ten days ahead (leaf fall risk, low adhesion risk and wind throw risk);
- percentage leaf-fall that has taken place throughout the season, indicating its progression and predictions of 50% and 95% fall dates;
- hourly summaries providing detailed information of leaf-fall and low adhesion coinciding with peak travel times;
- text summaries of the causes of low adhesion.
Case study
Rail Operator, Translink, uses our leaf-fall prediction service. Find out more about our work with them to help reduce operating expenditure and increase efficiency by viewing the video or reading the case study.
To find out more about our leaf adhesion service, please email transport@metoffice.gov.uk
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