Analysis
RICHARD CLINNICK examines the seasonal problem of leaves on the line, and how NR approaches the task of keeping the tracks clear
Leaves on the line.
SURE as night follows day, so there will be stories in the national media about leaves on the line. It’s a classic headline that has almost become a joke, but for the rail industry it is no laughing matter.
Autumn presents a real headache for the railway. Track conditions as a result of the weather can be the cause of one million minutes of delay.
An example of the problem is highlighted in the Office of Rail and Road’s Passenger and Freight Rail Performance 2017-18 Q3 statistical release, published on February 22 this year.
It highlights that Public Performance Measure (PPM) failures attributed to ScotRail increased by 28% in the third quarter of 2017-18 (OctoberDecember) compared with the corresponding period 12 months earlier. It said this was “mainly due to an increase of 62% in external ScotRail causes including low adhesion and other autumnrelated causes”.
Timetables need to be changed, so that operators can factor in the dicey conditions that their drivers must contend with when driving trains on what is the equivalent of black ice. It’s not unusual for a driver to put the brake on and for the brake to be unresponsive.
There are also problems for passengers. For example, in East Anglia in recent years, various branch lines have had their services cut back (or even cancelled) for days on end due to the conditions.
If not treated, the leaves can cause severe wheel flats, resulting in trains being pulled from service to undergo urgent repairs. In a fleet of 26 trains, one or two out of traffic for this reason can be managed - but when eight or nine are withdrawn that becomes a major problem.
So, what actually happens?
Leaves fall from trees and land on the rail. These leaves then get flattened by trains, creating a slippery Teflon-like substance that coats the rail and reduces the ability of the train to accelerate or brake. Drivers must use simulators during the year to train for just such an occurrence.
With train performance affected, timetables must be rewritten because the train requires more time to brake and accelerate.
But that’s not all - signalling can also be affected by leaves. Signalling systems use electric currents to locate trains, but fallen leaves can make the readings less accurate by interrupting the connection between track and train. When that happens, the signallers lose where the train is,
and so have to stop others around them. As a direct result of this problem, Network Rail must leave longer gaps between the trains, leading to delays.
In the UK, some 50,000 hectares of railway land are home to millions of trees, bushes and other plants that shed leaves. According to Network Rail, a mature tree can have up to 200,000 leaves, and potentially all could fall on the railway.
From October 1, NR has been receiving adhesion forecasts twice a day from specialist weather forecasters, who highlight locations that require treatment. This enables Network Rail to better plan its resources.
To support its fight against the leaf problem, Network Rail has 61
trains in traffic until December. These operate across the country, at all times of the day and night. Some of the railhead treatment train circuits can take up to 20 hours to complete, and are operated daily. There are 32 multipurpose vehicles (MPVs) and 29 railhead treatment trains (RHTTs). These offer different duties, with the lighter MPVs able to serve locations the locomotive-hauled RHTTs cannot.
NR Route Delivery Director Rob Davis told RAIL on September 28 that the trains had begun running earlier than usual this year, as 2% of the leaves had already fallen by that day. Normally, the trains start in mid-October.
He explains: “We have been treating leaves in the autumn for decades, and we are acting from both experience and also from talking to the Met Office twice daily.”
Asked why the treatment has started earlier than usual, he replies: “We just want to make sure it is OK.” Davis added that weather reports tend to be refined every 24-48 hours.
NR has more than 350 specialist
modules that it uses to combat the autumn problem. It uses water jets to blast the leaves with 92 litres of water per minute at a pressure of 1500 bar. It’s that strong that if you were to place your hand under the jet, it would cut right through it! Likewise, the train must always be moving when spraying, otherwise the rail will be cut.
The other treatment is sandite, a gel containing sand and steel or iron shot, which provides adhesion for trains.
NR says that which module is deployed depends upon the needs of individual routes, but its arsenal of weapons against the weather includes 67 water jet modules, 108 adhesion modifier modules, 135 RHTT water tanks and 40 APUs (auxiliary power units that supply air and electric to the trains). One RHTT tank holds 17,000 litres of water, and a three-tank formation can work for 12 hours straight.
Last year’s autumn treatment covered some 1.7 million miles, which according to Network Rail
is the equivalent of travelling to the moon and back three and a half times. And the number of sites treated by the trains has more than doubled in the past decade. Davis adds: “There are lines that historically have more trees than others.”
The requirements vary from region to region, as you would expect. This year, NR says that in the London North Western region there will be eight trains covering 102,000 miles over ten weeks, spraying 32 million litres of water. In the Midlands, four trains will operate purely on the CrossCity lines, covering 6,000 miles in the same period, spraying one million litres of water.
There are other ways of dealing with the problems caused by the autumnal weather.
In Anglia, Network Rail has installed 43 traction gel applicators at high-risk locations on its route. These automatically apply traction gel to the track every time a train passes. This is then collected by
train wheels and is carried along - thus treating track and train at the same time.
There is also a ‘sand rover’ in use. This is a rail-adapted road vehicle specifically designed to scrub tracks with brushes and apply a layer of gel to treat the Sudbury line, during peak leaf-fall season. This is because RHTTs cannot access the branch easily. NR also has engineers along the route working all year to manage vegetation, so that when the leaves fall they create less of a problem.
On the operational side, to combat the problems of the past, Greater Anglia has had its Class 15x fleet fitted with wheel slip protection (WSP). This is the first time the technology, commonly found on new trains, has been fitted to Sprinters dating from the 1980s.
Vegetation clearance is currently an emotive subject, with the Woodland Trust criticising Network
Rail’s treatment of trees ( Comment, RAIL 863), and Rail Minister Jo Johnson commissioning a report into said actions.
Davis responds: “It is a balance. We need to cut the vegetation to make sure the railway is safe, but we have to balance it against the needs of the local communities.”
Once December 13 arrives, which is NR’s planned end date for the autumnal treatment, there is no rest. Attention then turns to snow and ice. The MPVs at Tonbridge, displayed to the press on September 28, will be used in that fight, as will the recently acquired Snow and Ice Treatment Trains (SITT).
For Network Rail, the battle against Mother Nature never stops. ■ In the next issue (published November 7), RAIL travels on a railhead treatment train to observe first-hand how the problem of leaves on the line is being tackled.