Looking after Metro’s trackside areas
We have a constant programme to manage vegetation alongside about 50km of suburban railway tracks we own and operate in Newcastle, North Tyneside, Gateshead and South Tyneside.
This page explains how we balance our overwhelming priority to operate trains safely and reliably for Metro’s 36 million passengers with the wish to preserve wildlife habitats and biodiversity as far as possible.
Lineside trees at South Terrace, Wallsend
Our overall plan
We have managed vegetation on Metro since it opened in 1980 and this includes cutting back and removing trees and bushes along the line on a cyclical basis. Much of this vegetation has grown and been cut back repeatedly since the 19th Century, changing constantly along with use of the railway over the decades.
We will, over time, carry out work across our entire infrastructure on Tyneside (the shared line south from Pelaw through Sunderland is owned by Network Rail) focused on the operational envelope of the railway. This is usually the area within 3.5 metres of the track though sometimes beyond this to allow us to maintain structures, deliver modernisation projects or deal with diseased or dangerous trees. Most of our embankments and trackside areas are wider than 3.5 metres, and we do not normally cut back trees and bushes on this wider fringe.
We must prioritise work which supports the safe and reliable operation of Metro. We get many requests each year from people who would like trees and bushes to be cut down behind their properties; we are normally unable to carry out this kind of work unless it coincides with vital railway maintenance, due to the limited resource we have and the need to prioritise safety-critical activities.
As our railway lines pass through suburban areas a significant amount of vegetation near the railway line is actually on neighbouring property. We work with neighbours such as homeowners and local councils to make sure this does not become a safety risk.
Why is vegetation management important?
If we do not control lineside vegetation trees and bushes will become a danger to passing trains, our staff and passengers, and members of the public using level crossings. The leaves they drop are also the cause of low rail adhesion, the main reason for delays to journeys each autumn.
In 2017 there were more than 1,000 incidents on UK railways where trains collided with fallen trees of branches. Incidents caused by vegetation cost £100m and delayed tens of thousands of passengers. Metro is no different to the rest of the railway network in this respect.
The removal of vegetation within 3.5 metres of the line also ensures that train drivers have a clear view of the route ahead including signals and crossings, and that track workers have safe places to stand when trains and maintenance vehicles pass. It is an essential preventive safety measure.
A mature tree can grow up to 50,000 leaves each year and along railway embankments are the single overwhelming cause of low rail adhesion. This is a phenomenon which sees leaves burnt to a hard Teflon-like paste on the surface of the rail by the hot and heavy wheels of passing trains; the line then becomes slippery forcing drivers to slow down to avoid skidding as they approach stations, and preventing acceleration when they leave. On Metro there are a large number of sycamore and poplar, and these large broad-leaved trees are particularly bad in this respect.
What kind of work takes place?
The four most common forms of vegetation management on Metro are:
Cutting back: Specialist contractors working with power tools will cut back all vegetation along one side of a line to ground level, within 3.5 metres of the line. Logs will be left in piles as a habitat for insects while lighter vegetation will be chipped and left at the site. This work may be done while trains are running, during night shifts or during a planned line closure; this depends on site safety assessments and whether it can be fitted into a line closure alongside other maintenance projects. The ground is left in a form that encourages regrowth of native species.
Flailing: We use a flail (similar to a very large garden strimmer) attached to a rail vehicle to remove lighter vegetation closest to the track. The flail can cover a longer stretch of track relatively quickly during a line closure.
Weed spraying: We spray the railway tracks themselves with weed killer each spring to prevent growth through the ballast.
Emergency work: At times a tree or branch will become an immediate danger to the railway, because it has fallen across the track or power lines or could be about to do so. Engineers will go out immediately, 24 hours day, to remove the danger.
We have, in the past, carried out pruning or pollarding to trees along Metro lines in order to reduce the immediate visual impact of our work by retaining a screen along the line. This has not proved effective: Trees dealt with in this way have become weakened and distorted, increasing the risk they will one day fall suddenly on the line or neighbouring property. Such work has also to be repeated frequently at increasing cost and complexity as regrowth occurs from established trunks and roots.
Preserving wildlife habitats
We recognise embankments are wildlife habitats and we take active steps to ensure they remain so and respect the biodiversity they represent, much of it a result of their status as operational railway land. While railway safety comes first there is much we do to look after our wildlife.
Vegetation Management is carried out for Nexus by specialist contractors with experience of the railway environment and in line with all relevant British and European safety legislation. We take steps to identify and protect bat roosts and nesting birds and to do as much work as possible outside the nesting season, between September and March. Where an active nest is identified during work in season contractors will leave it undisturbed, if necessary returning at a different time of year. We liaise with local councils when carrying out work in designated conservation areas, while protected trees are managed in accordance with legislation.
Where ground is cleared log piles are left to provide homes for insects and small rodents, and we encourage the regrowth of native hedgerow species such as hawthorn, holly and blackthorn. We will carry out selective replanting to encourage hedgerow species which provide a denser foliage low down and good habitat for songbirds, in place of larger trees which present a greater long-term risk to the rail network.
Where at all possible vegetation management will be offset by two-three years on each side of a single stretch of line. This is to allow any fauna such as rodents and resident birds disturbed by our work to move across the track, maintaining the railway wildlife corridor along our lines. In places on Metro we have also worked with local communities to establish nesting boxes, bee hives and community gardens and allotments where we can do this outside the operational envelope.
While the visual impact of vegetation management can initially seem severe, in practice regrowth occurs rapidly. We have found that bushes and shrubs have regrown to a height of two metres (above the line of boundary fencing) within three years of clearance on Metro and Network Rail embankments in the area. There is a link on this page to an example of regrowth on a north-facing Network Rail embankment in Byker, Newcastle.
Consultation with our neighbours and impact assessments
When the work we carry out is for railway safety within the operational envelope of Metro we are only able to offer the minimum of consultation with neighbours – such as a letter informing that work is to take place and a route to ask questions or raise concerns.
Where vegetation clearance is planned for other reasons – for example because it is part of building a new station or line, or because it has been requested by residents – we will carry out full consultation and take account of the views expressed by all those who respond.
We will assess the impact of any maintenance project. In the case of vegetation management our primary consideration will be the impact on the tens of thousands of passengers who rely on Metro. We also consider the impact on wildlife, as described above, and on our neighbours when considering when and how a project will be delivered.
Our neighbours are sometimes concerned that cutting down trees will increase noise from passing trains. Research suggests that, in fact, vegetation provides no noticeable protection from the sound of a transport corridor unless it is planted densely to a depth of 15 metres or more – a greater width than on almost any part of the Metro network. Research also indicates that mature trees, taller than 10-12 metres, have less impact because the leaf density is above head-height.
We are conscious of the noise that vegetation clearance itself generates, through the use of power tools. We will carry out work during the day as much as possible, though at times we will work at night to reduce the need to close lines to passengers.