Leaves on the line
Every Autumn thousands of tonnes of leaves fall onto train tracks. This means one thing for a growing number of rail travellers – delays to their journey (1)(2).
Leaves on the line seems an incomprehensible reason for delays in this day and age. You might ask, how could leaves possibly cause a problem for a massive passenger train? Can't the rail companies just remove them with an industrial sized leaf blower on the front of trains?
This video shows how fallen leaves stick to damp rails, creating a slippery layer that reduces grip.
The problem stems from the fact that we are not simply dealing with crispy, wafer thin leaves on the track.
- Leaves fall on and around the track and as the train passes the aerodynamic effect will deposit more leaves on to the track.
- When the train passes over the leaves, the wheels compress them into a paste, with a force of around one gigapascal (30 tonnes a square inch), between the wheel and track.
- The leaves are transformed into a black Teflon-like surface (called a 3rd layer contaminant), that’s bonded to the track surface.
- This super slippery layer reduces grip, meaning trains need to accelerate and brake gently to avoid slipping.
Currently, the antidote is regular treatment, with very high pressure water jets (114 million litres of water annually) and the addition of an adhesion modifiying gel to increase grip.
In areas where this is not available, (rural routes often don't have the resource to run machinery over the tracks every few hours) they are typically cleaned by manual cleaning crews. This is effective but extremely labour intensive costing the industry and wider society around £345 million per year (3)(4).
Each of these treatments is good for about 200 axle passes (5), which on a busy line, equates to around two hours of trains. Given that the cleaning rigs might pass over every six hours at best, you can see there’s a lot of room for improvement.
In many areas the railway industry has innovated and improved provision hugely, especially when you consider how many more passengers it transports around the country since the 1990s. But in the area of clearing the leaves to maintain train times, it continues to struggle to solve the nationwide problem 24/7.
How does it work?
Our technology clears the residue on tracks, returning the surface to a dry, clean and uncontaminated state, enabling the trains to run as if it were summer all year round, leading to increased capacity and closer running trains (working towards RSSB targets). 6
Our early testing focused on microwave energy (see photo below) but more recently we have seen far superior results with plasma.
We now have a full-size working demonstrator that we are testing on rural network tracks in South Wales. The next step is to make the prototype available to busier networks for more thorough testing.
The ultimate deployment is to fit this to every passenger train, enabling train drivers to predict braking distances regardless of the weather or season and for network operators to increase the capacity on the miles of track they own.
Where did the idea come from?
When the Railway Safety and Standards Board (RSSB) put out an open call for innovators to tackle a challenge relating to track adhesion in 2016, we responded because we thought we had the solution. This ‘Predictable & Optimised Braking’ project, set up by the RSSB was an initiative drawing on a number of sectors, in a collective effort to solve the challenge of autumn delays and track cleaning. Our studio was tackling one area of it.
This project is a great example of how our team responds to challenging briefs, starting with our inhouse engineering expertise and working with others along the way to find the best solution. We started down one route which was inspired by a conversation we'd had twelve years previously when working with microwaves on a project for warming up frozen smoothies. Back then, we had discussed the potential for using pure microwaves to help solve the problem of leaves on train lines.
But it turned out, once we started testing our hypothesis, that pure microwaves weren't sufficient for the job, so part-way through, we pivoted to solve the problem, using new knowledge that came to light in a chance conversation.
The plasma discovery
After discovering through our first phase of research that pure microwave alone would not work as a solution on the metal rail head, we discovered with Industrial Microwave Solutions, that microwave energy could be converted into very hot plasma and we started to investigate this route.
After developing our Microwave Plasma System, we uncovered some research into DC plasma, that had been started by British Rail (BR) in the ‘70s. This was superb supporting evidence for us, to justify our pursuit of plasma treatment, but we needed to use alternate methodologies in our solution as the previous technology had faced several technical challenges.
In the beginning
Back in 2016, at the start of the project, ITV interviewed Mark and Julian, co-founders of The Imagination Factory, where they explained what the real problem was, why it was so difficult to solve and the novel approach that The Imagination Factory team was taking to solve this problem, using microwave technology. You can watch it here.
If you would like to know more about any of the work we are doing in this area, please get in touch with firstname.lastname@example.org
1. Numbers of passengers have doubled since the 90s. With 18 trains per hour in busy periods and 22,000 miles of track in UK, that’s a lot of room for disruption. Total franchised passenger journeys 1996-97 - 800M; 2016-17 - 1730M. Delays and unpredictable timetables report.
2. GB rail services were delayed by over 350,000 minutes due to low adhesion conditions last year, causing delays to millions of passengers and freight services. Reliable braking in low adhesion conditions could deliver a significant reduction in industry and wider societal costs associated with poor rail adhesion, which are currently valued to exceed £300M per annum.
Industry and societal costs include delay minute payments, prevention management and cleaning costs, rolling stock and infrastructure damage and safety costs. Sanders are routinely used on trains to reduce the impact of slippery rail head conditions, referred to as low adhesion. By blasting sand between the wheel and the rail, sanders improve the reliability and safety of train services. Read this article for more info on this story
3. Sand adhesion report
4. GB rail industry and customers encountered an annual average of 350,000 adhesion delay minutes over 2010 to 2016 – in the order of £275m.
Prevention, management and cleaning costs - £49m.
Industry costs associated with having an autumn timetable is £11m.
Cost of repairing rolling stock and infrastructure damage, as result of leaf fall is estimated at over £10m
5. p191 www.raildeliverygroup.com/component/arkhive/?task=file.download&id=469773735
6. Increased capacity on tracks – working towards meeting the targets set in the Rail Technical Strategy - Capability Delivery Plan