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Network Rail's vegetation problem

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Leaf fall timetables, defensive driving, RHTT runs etc etc etc.

They are not a 'solution' though, merely band-aids.
Leaf fall timetables are chaos.
RHTT runs are spending money to not fix the problem. Also, what happens if/when it gets worse, & the RHTT needs to run every day on each line, or the process simply stops working?


You really think the wholesale obliteration of every significant plant near the railway line would only be noticed by people who live adjacent to the railway?

And then there will be the vastly increased subsidies to pay for this never ending war against nature

There could be plenty of greenery along rail lines, it just needs to be appropriate.
Ground-cover bushes, evergreen trees, etc
 
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mr_moo

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There's some really promising developments re this using dry ice and other methods.

Article from September last year:

Rail Engineer has often written about the problems of low adhesion caused by, inter alia, leaf debris rolled into the railhead. As a reminder, dry leaf debris can cause wrong-side track circuit failures and, when wet, can lead to very low wheel-rail friction levels.
A coefficient of friction of approximately 0.2 will allow trains to brake normally, but wet leaf debris firmly rolled into the rail can deliver an exceptionally low coefficient of friction in the order of 0.01. To put this in context, the coefficient of friction in a well-lubricated car engine is circa 0.05.
Every Autumn, Network Rail runs Rail Head Treatment Trains (RHTT) to clean leaf debris from the rails. These trains blast the leaf debris, which by now has been firmly rolled onto the rail head by passing trains, with water jets at between 1,000 and 1,500 bar and then deposit sandite – sand with some ground metallic material suspended in a sticky paste. These trains carry a very large quantity of water and sandite, are very effective, but also use capacity on the network.
Are there better techniques for cleaning the rails? Could they be deployed on service trains to avoid the loss of capacity? This is something that the Adhesion Research Group (a sub-group of RSSB’s Vehicle Track System Interface Committee) has been researching for some time. Four alternative methods were presented in a recent webinar hosted by RSSB, and the number of questions asked after the presentations was testament to the interest in the topic.
Four techniques were presented: dry ice, plasma, laser and, lastly, a very surprising solution, given that conventional wisdom says water and leaves are part of the problem, not the solution – improved braking through controlled water addition.
Dry ice
Professor Roger Lewis from Sheffield University described the use of dry ice (solid carbon dioxide CO2) pellets to clean the rail. The principle is similar to the sand or soda blasting used to clean corroded steel; compressed air and the kinetic energy of the pellets bombard the contamination, although in this case, the thermal shock of the cold pellets makes the leaf film more brittle and the sudden expansion of the CO2 gas aids the removal of the leaf film.
Dry-Ice-Oban-1-1024x683.jpg

It is useful to recall that CO2 does not exist as a liquid at atmospheric pressure, transitioning from solid to gas or vice versa without a liquid state. The supersonic compressed air deals with liquids/moisture and the pellets deal with solid matter. The effect is merely on the surface of the rail and cooling of the rail is virtually non-existent. Even with the treatment train moving 16km/h, the rail head is exposed to the jet for only around 0.005 seconds. There is also no impact on cracks, insulated block joint end posts, ballast (allowing use on switches and crossings) and on the polymer around embedded rail.
dry-ice-Sheffield-trial-13-1024x577.jpg

Roger said that food grade dry ice could be delivered to depots as pellets (costing about £1/kg), made in depot or made on board the train. He added that the CO2 does not add to the carbon footprint as it is a captured as a by-product of other processes.
The concept was first tested using a road-rail vehicle (RRV) in the Sheffield Supertram depot. This delivered promising results, leading to trials on five different Network Rail routes around Oban, Squires Gate and Knighton (passenger) and Deepcar and Sutton Park (freight).
As an example, at Oban, the test site ran from Oban depot (next to Oban station) to just before Connel. On average, there were two cleaning RRV visits per day and they cleaned just under six miles of track, with extensive rail swab measurements being taken before and after blasting; double the distance would have been possible without the measurements.
Dry-Ice-Oban-3-768x1024.jpg

These trials consistently delivered bright rail heads, free from leaf film and, outside the running band, corrosion. Brake tests with a DMU delivered results on the cleaned rail that were at least as good as those on dry rail.
Roger concluded that cryogenic cleaning effectively removes oxide and leaf contamination from rails. It is a flexible technology that can be used manually, on a trolley or on an RRV.
Next steps include testing leaf clearing and braking at higher speed. This might include tests using University of Huddersfield’s full-scale wheel/rail HAROLD rig, followed by trials on Tyne and Wear Metro’s RHTT with the aim of optimising performance of the dry ice system for RHTTs.
There is also a plan to run a season long (10 week) cleaning trial on the West Highland line in Autumn 2020, to show the reliability of the RRV mounted system.
Finally, Roger wants to carry out more work to demonstrate the viability of fitting the system to passenger trains, reducing the effect on line capacity of using dedicated RHTTs.
Plasma
Julian Swan, co-founder and engineering director of the Imagination Factory, discussed clearing leaves using a zero-contact electrical plasma jet. This produces an intense but focussed energy ‘beam’ using electricity and compressed gas and no other consumable materials.
Plasma-trial-31-crop-1024x659.jpg

plasma-contaminated-rail-33-1024x861.jpg
Contaminated track.
As plasma is often used for cutting metals up to 150mm thick, the challenge is therefore to clear the leaves without harming the track, requiring a good control system. Turning off the plasma at slow speeds or when stationary also helps!
After successful laboratory trials, a demonstrator was installed and tested on a container flat wagon. This delivered further confidence in the system and led to a prototype using a road-rail vehicle towing a custom road-rail trailer. The photographs comparing the rail contamination before and after being cleaned demonstrate the effectiveness of the system after one pass. Julian said the results are cumulative, with any residual contamination being removed on subsequent passes of the plasma jet.
plasma-clean-rail-33-1024x850.jpg
Cleaned track.
As one might expect, the efficacy of the system depends both on the power of the plasma jet and the speed of the train. For a given speed, a 25kW plasma jet delivers “pretty clean” rail after one pass and “virtually clean” rail after two passes. In comparison, a 15kW jet takes four passes to deliver virtually clean rail.
Julian illustrated how the system could be applied to a range of scenarios, being deployed from RRVs at <10 mph, high speed RHTTs, passenger and freight trains at >60 mph.
He paid tribute to his collaborators: British Steel, Metallisation, Microwave Technologies Consulting, Industrial Microwave Systems, The National Physical Laboratory and Knorr Bremse.
The Laser Train
Ben and Harm Medendorp of Laser Precision Solutions (LPS) presented their solution – cleaning the rails with lasers using the Pulsed Laser Ablation technique.
The use of laser technology was first put on rails two decades ago, having been trialled on Railtrack infrastructure under the name Laserthor in 1997. LPS started work in 2016 with the usual laboratory and prototype testing, but, since 2018, the company has been working with the Long Island Railroad (LIRR, part of the Metropolitan Transportation Authority of New York) to help it solve its leaf contamination problems.
In 2018, LPS demonstrated successful rail cleaning, delivering three times higher adhesion after one pass of the laser at 12mph, against a target of 9mph. This convinced LIRR to commission LPS to produce a fully operational prototype, capable of operation from a non-passenger train at 25mph. This was deployed for 12 hours a day in autumn 2019 over extensive parts of the LIRR network prone to low adhesion. A reliability of 99 per cent was achieved.
The results were impressive. Compared with 2018, LIRR reported a 17 per cent reduction in low adhesion events on the whole network and 65 per cent reduction on the lines where LaserTrain operated. There was a two per cent improvement in punctuality, 65 per cent fewer late trains due to “weather”, 32 per cent fewer short trains and 48 per cent fewer cancellations (the latter two points due to fewer units awaiting wheel flat repairs).
laser-installation-4-1024x768.jpg
LaserTrain installation.
With fuel or any other source of energy as the only required input (35kW system consumption), the LaserTrain, logistically, is easy to implement.
The next stage is to scale the system so that it can operate at line speed (approximately 60 to 70mph). The required laser technology is ready and LPS is looking for a partner to put it to good use.
Water-Trak
At first sight, it seems odd to add water to slippery rails, but, of course, that is exactly what the RHTT does, leading to the questions “how much” and “when”?
John Cooke of CoCatalyst and Simon Barnard of SCB Associates explained: “The role of water in creating low adhesion is now well understood. We know that a dry track will deliver the highest level of adhesion. Wet track, while having a lower level of adhesion, will still give acceptable braking performance. When a critical amount of water (microlitres per metre) is present on the railhead together with contaminants (such as compressed leaf matter or iron oxides) the adhesion value can reduce radically (down to 0.01 to 0.02) resulting in very poor braking and traction. Water-Trak aims to move the railhead away from this highly undesirable condition by adding water.”
Water-HAROLD-trial-47-768x1024.jpg

Introducing between 1ml/metre and 4ml/metre of water into the ‘nip’ between the wheel and the rail is enough to deliver this effect. Using Huddersfield’s HAROLD rig, a test of braking on a leaf layer led to significant wheel slide, with WSP (wheel slide protection) activity lasting for over 30 seconds. When water was introduced, the duration of WSP activity reduced by nearly two thirds. In addition, the tests results showed a significant improvement in wheel and track cleaning, indicating the potential of Water-Trak as a rail head treatment solution.
The speakers said that the current water system has a capacity of over 200 litres for both rails, giving a total dispense time of over 30 minutes. One system would be provided at each end of fixed formation trains. If water is delivered only on WSP activation, they estimated that the water would last for 1-2 weeks of operation, depending on the adhesion encountered by the train. If it was decided that there is a cleaning benefit to be derived from delivering water every time a train brakes, then the 200 litres of water would be sufficient for more than one day’s operation.
As to effectiveness in combination with sanding, a study by the University of Sheffield has shown that sanding performance is significantly improved when delivered onto a wet track; water helps to retain more sand on the rail. Water-Trak delivers water to the leading axle of the train so pre-wets the rail ahead of sand application. As the water does not interfere with, and may even enhance, the performance of track circuits, it also extends the operating envelope of low adhesion mitigation – it can work down to zero speed and in all locations, including points and crossings.
John told Rail Engineer that it is not yet clear if slip between the wheel and rail due to braking is key to the removal of contaminants. One possibility is that water softens the leaf layer, allowing the mechanical action of the wheel rolling on the rail, together with the high pressures generated, to accelerate its removal, remembering that parts of the contact patch will be experiencing creep due to wheel-rail deformation even when the wheel is just rolling on the rail. He added that CoCatalyst plans to run some further tests in which water is added without braking to explore this phenomenon.
John also acknowledged that they have more work to do to make the system suitable for freezing conditions!
In summary, this is a simple, low cost, low risk system that can improve traction and braking for following trains, so the benefits of fitting a lot of trains is cumulative.
Conclusion
The four techniques presented here have all demonstrated that they can effectively clean leaves off the rails. They are all at different levels of development – some have a degree of practical experience in improving adhesion on operating railways, whereas others have yet to emerge from the laboratory.
As always with these R&D projects, Rail Engineer will return to the topic as the projects progress.

Note: for more information on the plasma and laser processes, an examination of the Wikipedia articles on plasma cutting and laser ablation outlines some of the science.
Thanks to Paul Gray, Giulia Lorenzini and Ben Altman of RSSB, together with the presenters, for their help in preparing this article.

And a more recent update on those same issues:

In our last edition, we reported some of the highlights of ADHERE 21, work sponsored by RSSB and the industry’s Adhesion Research Group (ARG). There was too much to cover in one article so here is the remainder, focussing on rail head cleaning and dependable speed measurement.
Three presentations were made on progress with developing alternative methods of cleaning rails compared with the current Rail Head Treatment Trains (RHTT) which apply water jets at 1,000-1,500 bar pressure.
Dry ice
Roger Lewis, University of Sheffield, reported on the dry ice project. Briefly, this system fires dry ice pellets at the rail head to clean off leaf contaminant and iron oxide. In autumn 2020, the equipment was installed on the Nexus (Tyne and Wear Metro) RHTT and ran for four days over sections of line notorious for poor rail head conditions. A successful test was also carried out on a Northern Trains Class 155 unit at 40mph in March 2021.
Roger described options for obtaining the dry ice, including delivery, manufacture in the depot and manufacture on the train. The latter needs more development. The RHTT test involved continuous application, but Roger said that future work would explore other options including using a form of machine vision to trigger cleaning based on estimated rail head contamination. He also plans tests at the University of Huddersfield’s Institute of Railway Research (IRR), using its HAROLD test rig at the equivalent of 60mph, and a service trial on a Class 155 unit in autumn 2021.
Capture-2.jpg

Plasma Track
Roger Gray of Plasma Track outlined progress with a large Road Rail Vehicle developed by his company which uses a 100kW twin treatment system and was tested in the laboratory to confirm the power-to-speed relationship, demonstrating that an instantaneous surface temperature of >300C can be delivered for leaf removal and >900C for still more aggressive removal.
On-track trials were successfully carried out in autumn 2020. Plasma Track is confident that the system is scalable and proposed two variants for autumn 2021: a 15kW system on a road-to-rail truck for possession use, running at 10kph and delivering a 45mm-wide clean band to replace manual cleaning crews, and a larger 300kW system on a Multi-Purpose Vehicle or RHTT, with most of the equipment in a 20 feet long container. This would be capable of running at 80-100kph and deliver a 45mm-wide clean band. Both systems would be self-contained and use atmospheric-generated nitrogen gas, avoiding the need for compressed nitrogen bottles.
2A-1-1024x287.jpg
2B-1-1024x684.jpg
The cryo rail-cleaning train and nozzle.
For the future, Plasma Track is planning a passenger train system. This would be miniaturised and optimised to allow predictable braking. For this application, the system might clean a 10mm-wide band aligned with the wheel/rail contact patch. Several of these might be installed along the train.
Passenger and freight train-mounted systems would be active during braking/acceleration, replace sand applicators, require no consumable materials, clean the track for following trains and provide a cumulative effect for the entire network. The system could also be used for wheel tread cleaning.
Water-Trak
John Cooke and Simon Barnard from Water-Trak Limited described progress with their innovation of adding water to help adhesion, something that still feels counter intuitive despite evidence that it works! They explained that wet rails give good adhesion, but damp rails – especially if contaminated – provide very low adhesion. The system has been demonstrated at Long Marson on the Hydroflex train and was fitted to a Northern Trains Class 319, running for over 16,000 miles during autumn 2020, even though the system was only operated over four nights in a Signal Protection Zone between Prescot and Bryn.
3-3-1024x683.jpg
Plasma rail cleaning in action.
The system was triggered by Wheel Slide Protection (WSP) operation. There were three nights of severe contamination and one of moderate contamination. Results for runs between Garswood and Bryn showed significant improvements in both acceleration and braking performance when water was added, noting that the Class 319 with only 25% axles motored has a reputation for struggling to accelerate in poor adhesion conditions. Noticeable improvements to the achieved brake rate for Step 3 demand were observed when using water and the effect was cumulative.
Water-Trak plans to target operators of two and three-car trains for retrofitting with the system. Their trains are not prioritised for the fitment of Double Variable Rate Sanders. John Cooke noted that wetting the rails does seem to improve the performance of the sander systems as more sand sticks to the rail. They aim for an installed price of £30,000 for two systems, one at each end. Each system would have a capacity of 200 litres of chlorinated water from the same source as that used to replenish on-train toilet systems. Water-Trak estimate a payback period of approximately 4-5 years.
Dependable speed measurement
Julian Stow of IRR described the benefits of a dependable speed measurement system. WSP systems typically derive their speed signal from axle-end tachogenerators that measure wheel rotational speed. In the event of wheel slip or slide, the wheel rotation speed remains accurate, but the link to train speed is broken. WSP systems generally take the speed signals from all four axles on a vehicle and use these to estimate train speed, but that speed is probably different for each vehicle in the train.
The ability to control wheel slide depends on the accuracy of and the time taken to establish the estimation. Julian said that simulations carried out using the IRR’s low adhesion braking model, LABRADOR, showed that a reliable, accurate speed signal provided to all WSP systems could reduce a train’s stopping distance by up to 100m when braking from a speed of 20m/s (72kph).
Capture-3-1024x687.jpg
Result of Water-Trak test showing significant improvement in both acceleration and braking on Laps 2 & 3.
There are other ways of measuring speed including Global Navigation Satellite System (GNSS) radar and accelerometers, though each of these has disadvantages in a railway application. Ideally, speed would be measured in several different ways, but only use the most reliable speed signal for the prevailing conditions.
The automotive industry increasingly uses inertial measurement devices for accurate speed and for stability control/ABS etc, using just such a ‘real time sensor fusion’ approach to speed measurement. The decision on which speed measurement is ‘most trustworthy’ is made using an algorithm known as an ‘extended Kalman filter’ within the sensor itself. To provide the best performance in different applications, a range of motion profiles are available that optimise the Kalman filter.
Speed tracking
IRR undertook tests on an Inertial Navigation System from SBG systems that included a three-axis gyroscope, three-axis accelerometer and three-axis magnetometers, with external inputs for dual GNSS and an external tachometer. Over 45 runs, tests were carried out on a four-mile section of the Great Central Railway at speeds up to 110kph using a Class 45 locomotive. Although the sensor doesn’t currently have a rail-specific motion profile, it was found that good results could be obtained.
5-3-1024x680.jpg
The Huddersfield IRR team and Class 45 loco on the Great Central Railway.
Julian presented the interim results, showing a very close fit between the tachometer-derived speed and the estimated speed. The testers induced simulated sudden reductions in wheel speed – the tachometer signal – during braking and monitored how well the estimated speed tracked the true train speed. Even with the sensor using a non-rail motion profile, it was able to accurately estimate the speed for some 25 seconds and, when tachometer variations corresponding to the typical reductions caused by poor adhesion/WSP activity were induced, the estimated speed tracked the actual speed very accurately over the full braking distance from 110kph.
Julian concluded that commercial off-the-shelf inertial sensors show considerable promise in this application. Accurate speed estimation could be obtained on-train during simulated WSP operation, even without using a rail-vehicle-specific motion profile. Application-specific tuning of Kalman filters would further improve accuracy and this would also reduce time taken to initiate/align the inertial sensor. Decisions on which speed signal to trust could also be enhanced considerably with some simple logic. Applications include improving performance of current/legacy WSP systems, providing a speed signal to sanders etc without an interface to train systems and/or providing a reliable speed signal for ETCS.
And finally
Neil Ovenden, chair of the ARG, congratulated everyone on their work and presentations. He also issued a reminder that although these presentations were about improving braking performance, it is still important to clean contaminant from the rails everywhere. Damp, contaminated rails cause poor adhesion, but dry contaminated rails can result in wrong-side track circuit failures and these can cause dangerous occurrences, as illustrated by the RAIB report into the level crossing near miss at Norwich Road in 2019.
Thanks to RSSB and the speakers for their assistance in the preparation of this article.

So actually there's some great progress being made and if these can get to a point where they are fairly simply deployed on service trains, especially with targetted areas of treatment, then the response can be much better than just cutting down vegetation.
 

notverydeep

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Probably overly optimistic, although I hope I'm wrong. NR have the likes of the Woodland Trust, local Green Party organisations and a big NIMBY factor to contend with when carrying out necessary vegetation clearance.

As long as care is taken during the nesting season (when contrary to many assertions vegitation control for safety reasons may still be carried out), generally nature / conservation groups are fairly understanding.

In my experience, far more problematic are neighbours of the railway who have grown used to effective screening of the railway at the bottom of their garden (in many cases a screen that was present when they moved to the property), and do not want the intrusion, especially the noise when such a barrier is removed. Relationships with neighbours and stakeholders are not helped by the industry's vegitation clearance strategy being visit a section only once every 30 years with napalm and a bulldozer, but forget about it in between! Little and often would achieve the same end over a year or two, but with far less stakeholder management required...

Other key problems can be controlled species such as Japanese Knotweed or trees infected with Oak Processionary Moths, that require special attention to avoid being spread to other areas by clearance processes.
 

Railwaysceptic

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You really think the wholesale obliteration of every significant plant near the railway line would only be noticed by people who live adjacent to the railway?

And then there will be the vastly increased subsidies to pay for this never ending war against nature
There is no likelihood of "every significant plant near the railway line" being removed because even in most urban areas there is as much vegetation outside the railway's boundary as there is inside. The one exception to this generalisation is vegetation sprouting out of railway architecture in mean, inner city districts with no trees in the street. The majority of people in this country place a far higher value on safety than on sampling vegetation in inappropriate locations. Tackling the issue thoroughly will include dealing with the huge and increasing problem of damage being done to railway infrastructure by plants embedding themselves into walls, viaducts etc. The cost of not taking action will almost certainly be greater than the cost of proceeding in good time.
 
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Hellzapoppin

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they can't even clean the lineside scrap rails and building waste left everywhere, shame they cant have some sort of scrap wagon with a small crane, might not be easy with overhead cables
This is simply because there isn't enough time during possessions to get rid of the scrap.
I don't think people realise how difficult it is to access the infrastructure now, the days of just rocking up on site, appointing a lookout and starting work are long gone. Work has now planned to be done at night with line blocks or during possessions and everyone's trying to get in on those. On several projects I worked on we were lucky to get 3 hours a night to do anything, let along perform Alan Titchmarsh duties.
 

JKF

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Not certain this is the right thread for this (mods feel free to move or create a new one), but can anyone explain how the scheduling of RHTTs works? Are these planned in advance or to some extent adapted to conditions and weather? Is there a controlling mind somewhere making these decisions? Are paths in the timetable allocated and then services run when required, or should they be running whenever a path is shown in the timetable? I know on some of the local lines near here that runs are frequently cancelled, but I don’t know if this is by design or due to current issues with staff shortages etc.

With regards to the Salisbury crash I can foresee the press picking up that the previously scheduled RHTT didn’t run, but this might be quite normal with paths only taken if someone decides there is a need (clearly there was here).

Leaf fall isn’t something that happens with any degree of regularity, depends on species, seasonal weather and wind. I have to do leaf clearance as part of my day job, this week there was a huge amount of leaves and debris from the stormy weather at the weekend, but then barely any leaves fell across the site until this morning, three days later. I guess all the loosest ones had been blown down and it took a few days for some of the remaining leaves to ‘ripen’ and fall. It must be hard to plan around such inconsistencies.
 

boing_uk

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Empirical lab testing has found that trees do indeed increase slope stability with the largest effect at around 30 degrees and up until a 60 degree incline is reached, for slopes at or in excess of 60 degrees then trees may indeed be detrimental.
It really depends on the type of tree and the type of soil conditions in which they're growing, whether they're planted or self-seeded etc etc.

Different species have different root ball spread (some go outward, some go downward etc) different water take-up etc which all affect how they may or may not stabilise the ground in which they're growing.

Removing fully grown trees can also have adverse effects, particularly around groundwater, so it's never a clear cut. I've seen terrific ground heave following mature tree removal due to groundwater changes, but I've also seen fairly mild slopes dragged down by trees due to underlying subsoil weaknesses.
 

GRALISTAIR

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It really depends on the type of tree and the type of soil conditions in which they're growing, whether they're planted or self-seeded etc etc.

Different species have different root ball spread (some go outward, some go downward etc) different water take-up etc which all affect how they may or may not stabilise the ground in which they're growing.

Removing fully grown trees can also have adverse effects, particularly around groundwater, so it's never a clear cut. I've seen terrific ground heave following mature tree removal due to groundwater changes, but I've also seen fairly mild slopes dragged down by trees due to underlying subsoil weaknesses.
There are loads of photos in the now closed Manchester - Blackpool electrification thread where at Poulton-le-Fylde and other areas the trees were completely cut down but the bottom of the trunk and the roots were left in but poison pellets put in the stump so they could not grow back. I will try and post a few photos when I get time.
 

Nicholas Lewis

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This is simply because there isn't enough time during possessions to get rid of the scrap.
I don't think people realise how difficult it is to access the infrastructure now, the days of just rocking up on site, appointing a lookout and starting work are long gone. Work has now planned to be done at night with line blocks or during possessions and everyone's trying to get in on those. On several projects I worked on we were lucky to get 3 hours a night to do anything, let along perform Alan Titchmarsh duties.
This is very true on mid week nights and if your in electrified territory you lose even more time but i do find it equally frustrating when weekend abnormals are on no opportunity is taken to get the lineside cleared up. Main works contractor could help but don't want to get involved as ist not part of there contract despite they often have RRVs and plenty of staff on site that could undertake clearance.
 

Brush 4

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Just cut down the trees, which I know belongs to another thread but, is relevent to the general issue of the accident here.
 

GC class B1

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Or just cut down the trees, which I know belongs to another thread but, is relevent to the general issue of the accident here.
There seems to be a view that only leaves cause low adhesion. I was witnessing some braking tests on lines that were clear of leaf debris as they had been ground recently. Adhesion was fine until it began to rain, the rain was light but adhesion reduced straight away as shown by the increased stopping distances as WSP operated.

Also many years ago myself and a colleague were carrying out stopping distance tests with a composition braked locomotive and cast iron braked coaches and we noticed a clear reduction in brake performance when it snowed. As Cast iron brake blocks are not particularly affected by moisture this must have been mainly down to reduced retardation from the composition brake blocks on the locomotive.
 
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Moonshot

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There seems to be a view that only leaves cause low adhesion. I was witnessing some braking tests on lines that were clear of leaf debris as they had been ground recently. Adhesion was fine until it began to rain, the rain was light but adhesion reduced straight away as shown by the increased stopping distances as WSP operated.

Also many years ago myself and a colleague were carrying out stopping distance tests with a composition braked locomotive and cast iron braked coaches and we noticed a clear reduction in brake performance when it snowed. As Cast iron brake blocks are not particularly affected by moisture this must have been mainly down to reduced retardation form the composition brake clocks on the locomotive.
Leaves on the line are responsible for the vast majority of slides. Therefore removing trees would alleviate a lot of problems
 

O L Leigh

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Leaves on the line are responsible for the vast majority of slides. Therefore removing trees would alleviate a lot of problems

I disagree as that's not been my experience. Leaf contamination can reduce adhesion, but the most common cause of the slides I've experienced (and slips as well, for that matter) have been weather related; mostly moisture in the guise of mist/fog or fine rain.

Removing trees will not banish low adhesion to the dusty pages of history. It's something that will be here to stay for as long as there are trains.
 

Llama

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If you drive to the expected conditions and you have a good driver's spider sense then you should rarely have any real problems caused by leaf fall. Industrial stuff, kerosene near airports, road salt at level crossings, flange lubricators, tree sap, soap, even greenfly can have an effect on adhesion and that's not including just the general atmospheric dust that settles on the railhead and can make it potentially treacherous in the first rainfall when it's not rained for weeks. We had a few overruns on the Chat Moss a year or two back because wood pellets from one of the Drax trains were apparently coming out of one of the hoppers and getting crushed on to the rail causing similar contamination to leaf deposits that get crushed on.
 

quattromatt

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I disagree as that's not been my experience. Leaf contamination can reduce adhesion, but the most common cause of the slides I've experienced (and slips as well, for that matter) have been weather related; mostly moisture in the guise of mist/fog or fine rain.

Removing trees will not banish low adhesion to the dusty pages of history. It's something that will be here to stay for as long as there are trains.
We’ve had major tree cutting back down here in Cornwall and railhead conditions are markedly improved so far this slippy season.
 

Moonshot

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We’ve had major tree cutting back down here in Cornwall and railhead conditions are markedly improved so far this slippy season.
Same up here in certain areas. You would have to wonder why Network Rail actually spend money blasting the rails with high pressure jets if leaves were not a significant contribution to slippy rail conditions. Of course back in the days of steam, vegetation wasn't anything like what it is now. I note HS2 embankments are getting covered with vegetation that doesn't grow more than 5 feet tall.
 

O L Leigh

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In the cab with the paper
We’ve had major tree cutting back down here in Cornwall and railhead conditions are markedly improved so far this slippy season.
Same up here in certain areas. You would have to wonder why Network Rail actually spend money blasting the rails with high pressure jets if leaves were not a significant contribution to slippy rail conditions. Of course back in the days of steam, vegetation wasn't anything like what it is now. I note HS2 embankments are getting covered with vegetation that doesn't grow more than 5 feet tall.

Great!! But that's not exactly what I was saying.
 

godfreycomplex

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I disagree as that's not been my experience. Leaf contamination can reduce adhesion, but the most common cause of the slides I've experienced (and slips as well, for that matter) have been weather related; mostly moisture in the guise of mist/fog or fine rain.

Removing trees will not banish low adhesion to the dusty pages of history. It's something that will be here to stay for as long as there are trains.
It’s very dependent on the area of the country and the prevailing weather conditions as to what the pre-eminent cause of slides is. I’ve signalled heathland areas with high wind and seawater risks and I’ve also signalled tree infested areas with relatively stable weather, and despite the causes being different, both were about as slidy as each other.

The difference is removing the sea may take a little while.
 

D365

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Another programme on Radio 4 , yesterday lunchtime- about trees in Sheffield. People love 'em- you'd think they, like us, will never die. Swampy lives on.
Trees have been a talking point in Sheffield for at least the last 12 years.
 

BrianW

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Trees have been a talking point in Sheffield for at least the last 12 years.
Not just Sheffield is my point- everyone loves trees, as Swampy and others have demonstrated over the years. They are more important than that people should have places to live, or than HS2. NIMBYs love trees.
 

Robertj21a

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Perhaps I'm being silly, or just missed a point. Just how far away from the rail is a tree likely to be 'safe' ? - presumably, it's largely dependent on the type of tree and leaf ?
Don't leaves blow for a fair distance in winds?
Won't a lot of trees be in private gardens ?
Apologies if all this has been answered, or simply more obvious to other people.....
 

JKF

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the general atmospheric dust that settles on the railhead and can make it potentially treacherous in the first rainfall when it's not rained for weeks.
That also affects roads, especially block paving, makes it kind of ‘greasy’, especially with a fine drizzle. Found this out to the cost of a broken arm when someone wandered into the path of my bike and I had to make a sharp application of the brakes.
 
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