Leaves on the line.
RICHARD CLINNICK examines the seasonal problem of leaves on the line, and how NR approaches the task of keeping the tracks clear
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 In a fleet of 26 trains, one or two out of traffic for this reason can be managed - but when eight or nine are withdrawn that becomes a major problem.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