TRANSPORT for London (TfL) is the integrated authority responsible for meeting Mayor Sadiq Khan’s Transport Strategy (2016–2025) commitments, including (under the Healthy Streets delivery framework) a target that 80 per cent of all journeys will be made on foot, by cycle or public transport by 2041.

TfL’s road network comprises 580 kilometres of ‘red routes’ lined with 24,300 street trees and 200,000 m3 of woodland. Each year, TfL’s tree inventory removes nearly 6.3 tonnes of air-borne pollutants, store over 6,700 tonnes of carbon and diverts an estimated 8,700 cubic metres of storm water run-off away from the local sewer systems. These Highways (‘open networks’ accessible to the public), account for 5 per cent of London’s road yet carry 30 per cent of the traffic.

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In April 2021, in one of the UK’s most prominent Highways contracts (worth £1.7 billion), TfL and three infrastructure contractor partners (Ringway, FM Conway Limited and Tarmac Kier JV) united under one eight-year citywide Works for London programme to maintain all roads, bus and street assets.

Working within the Engineering directorate and through Highways Asset Operations (the team that raises works orders and liaises with onsite contractors), the Green Infrastructure team provides technical support to the partners on all matters relating to Green Infrastructure asset types.

Management of TfL’s Green Infrastructure asset types for Highways is divided into three geographical regions: North, Central and South. Aside from Lambeth, Southwark and Wandsworth, South covers most boroughs south of the River Thames down to the M25, including Greenwich, Lewisham, Bromley, Croydon, Sutton, Merton and Richmond, including gateways such as the A2, the A3, the A20 and A23, or “all primary roads that are not motorway and a 28-kilometre off-road tram network,” says senior arboriculture and landscape specialist Grayham Tindal.

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Grayham has managed South since April. “My role is definitely unique. As I interpret the model, we are technical specialists providing support across the business on the day-to-day management of trees and landscaped areas. We also work closely with the Project teams to ensure TfL delivers effective protection to existing assets and enhances our Green Infrastructure assets. It is a 50/50 split. Within the function, we support colleagues in Asset Operations where a third-party development may or may not impact a tree/soft landscape and the approach TfL takes in discussions on how this should be managed to support the development. We are not directly involved with some of the administration tasks (overseeing contractors work orders). We don’t deal with Planning in the same way as Local Authorities – we can’t put conditions (TPOs) on trees – but we do comment on proposals and developments adjacent to Highways that may affect TfL assets.”

The traffic volumes on TfL’s roads mean that all red route arboreal assets are considered high-risk and managed for safety. “We also consider the wider benefits they provide to the capital’s residents and users.” Inspections including highlighting trees owned by third parties that may pose a risk are performed by road corridor and inspectors take approximately three months every year to survey.

Providing technical support on inspections means “preliminary meetings onsite with the surveyors and doing desktop exercises on the data they send back weekly. Once a week, we go out and perform percentage assurance audits on the inspections undertaken, to reassure TfL that the contractor inspectors (Conways) are providing accurate information and proportionate works, or to highlight any gaps in the information provided, simple works like low branches that may have been missed. In the last few months, I can only remember being informed about two near misses where trees failed, their collapse related to fungal decay. It highlights that regular inspections are necessary to ensure the tree stock is healthy.” Grayham also advises on grass verges and planted areas.

TfL’s arb cycle is similar to those of most local authorities: “Safety inspections during the summer, works delivered through the autumn, planting in the winter.” All remedial works identified are carried out in 24 hours, 7 days, 28 days, 3 or 6 months. “We do a 5–10 percent safety audit of works. If we are not satisfied, we can severely increase the audit ratio.”

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There are approximately 8,000 street trees in South. “Trees growing near bus depots and [TfL-owned] buildings were previously managed under a separate contract. We will start pulling in that data over the next 12 months.”

The tree stock is “a mix of oak and ash and smaller species, hawthorn, apples, birch and woodlands, linear features usually 5–30 metres wide planted on embankments adjacent to the roads during construction and focussed on screening and reducing noise and pollution.”

The ‘Healthy Streets’ framework aims to make London’s roads more welcoming for users and green infrastructure (planting and vegetating) is a key component. For Grayham, this could mean involvement in Projects such as Cycleways, along some of the 260 kilometres that have been delivered since May 2016. “It is about being involved as early as possible within the design process, to either argue the case for tree protection or the best mitigation packages to enhance the green infrastructure on the network as part of that scheme.”

Most projects undergo arboricultural surveys, ecology surveys and the creation of a biodiversity matrix “to calculate the units dependent on the habitat type. You evaluate the existing habitat type or biodiversity value of the area and then assess what you are proposing. Hopefully that gives a net gain figure.”

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We meet near to a double decker bus selling frozen yoghurt close to the London Eye on a day in early June that sees the capital’s thermometers rise steadily to a peak of 29.7 degrees. It is the hottest day of the year so far and the trees that shade a grassy hummock in Jubilee Gardens provide a cool place for a socially distanced chat.

For this writer, after months of working virtually, meeting anyone face-to-face is sensory overload. When asked to explain how his role works under the new Works for London contract for a fourth time –yes, really – Grayham remains patient and good-humoured.
Jubilee Gardens is a five-minute walk from Grayham’s hot-desking office in Palestra House. Pre-pandemic, he spent two days there and three days out on site. From being furloughed for 2.5-months during Lockdown 1, working from home and virtual Teams meetings are the ‘new normal’ and site visits are down by 80 per cent. “The Operations team go to site and take photos and we try and make a judgment on that information. When restrictions lift, we will see how the business adjusts. There is talk of reducing the time required in the office.”

Before the pandemic, nearly half of TfL’s income came from passenger fares. Pandemic movement restrictions saw the number of journeys made on public transport fall by 90 per cent. Conditional government bailouts, proposing budget cuts of nearly 40 per cent, made up the shortfall.

“This morning’s Teams meeting was with 14 colleagues, discussing the challenges TfL faces in the next 6–8 months.” Government bailout conditions include the impact to employee benefits, the potential of job security and the expectation that TfL becomes self-sufficient again by 2023. “We checked on everyone’s health, well-being, and feelings of inclusion (a key policy for senior management). I then wrote a draft specification for works for an alleged tree root damage claim (subsidence), another job we support within (Highways Asset) Operations.”

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A staff benefit used today, surely the envy of every Londoner, is an Oyster Card that offers free travel across London. Grayham’s favoured item of TfL merchandise is his Trams mug. The tram network connects Croydon to Wimbledon, and in peripheral areas it offers passengers a view of woods and farmland.

Originally from Lockerbie, Grayham, now 42, wanted a career in either farming or forestry. Choosing forestry, he gained a BSc in woodland management from the University of Central Lancashire. He worked as an establishment-phase contractor and contract forester for local estates before changing career paths to arboriculture. Moving to London to work with Trees for Cities, he then worked with Islington council as an urban forester. “The most important lesson was learning the value of public engagement and support, for them to understand the objectives of the work you do. You have to consider the views of others when working in the public sector. Understanding how local authority structures work is also useful.”

He joined TfL in 2015. “I was first employed to oversee contractors. Moving to Engineering, I provided support to Central, North, and now South. I like to talk about the whole of the network: I’ve covered most of it.” 

Still in the transition period between old and new contracts, he remains involved in earlier projects, especially around new planting. “The mayor’s ‘Transport Strategy’ looks for a 1 per cent (230 trees) increase annually. We have to balance that with our replacement tree programme (restocking between 250–300 trees a year for those removed for safety or other reasonable grounds), but as far as I am aware, we are on target.”

Planting alongside Highways, considerations such as road speeds (40 mph or less) carriageways require a visual clearance of 50 metres; 70 mph carriageways, 150 metres) and not impeding vehicles on that carriageway must be taken into account. “We plant reasonably-sized trees (14–16 cm or 18–20 cm girth), at least 700 mm to a metre back from the kerb face. We consider ground space and air space, planting down 6-metre spacing for smaller, upright-form species.”

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High traffic areas, such as Archway Gyratory, benefited from Pinus radiata and Magnolia grandiflora. At Highbury Corner, Celtis occidentalis, Cladrastis kentukea, Halesia Carolina, Monticola and Maytenus boaria. “Over the next couple of years, we will be focussing on the gateway areas and roads coming into London.”

On the executive committee of the London Tree Officers Association (LTOA) for the next two years, Grayham is working with eight partners on the London Urban Forest Plan, how it is managed collectively to enhance it over the next 5–15 years. In 2016, an i-Tree report estimated 2,367,000 tonnes of carbon to be stored by the majority of London’s trees, valued at £147 million. Ongoing discussions include whether it is better to use drones or helicopters to map and assess tree condition and health.

The TfL road network contains a relatively small proportion of ash (approximately 7.5 per cent). “To date, ash dieback has not caused a significant issue, but TfL will continue to monitor and follow guidance on how best to manage this disease. During spring, oak processionary moth surveys are ongoing. Previously, South recorded 40 locations. On the tram network, I recorded six trees’ locations in the last year. We continue to actively manage it by informing the Forestry Commission and then taking the appropriate action, first treating chemically if we can. If we miss the window, we remove the nest material and assess the following year on the need for more treatments.” 

In areas of shrubby landscape, TfL is trialling alternative methods of weed control, electricity or hot water and soaps. “We are reducing the use of chemical weed controls within the public realm, I hope that the public will recognize the benefits of this approach and come to accept that in some areas, it may not look so clean and polished.”
The public’s response to landscape management can vary. Vegetation clearance along one of TfL’s ‘closed’ networks was described in the local press as ‘environmental vandalism’. Grayham has more experience of complaints over arboricultural encroachment. “Because we don’t remove that many trees, we get more enquires as to whether we can prune or remove them. Residents adjacent to a tree may complain over issues like roosting pigeons. When they foul and it lands on their car, they want the tree removed. We wouldn’t agree to this type of request and would explain the reasons why this wasn’t necessary. However, if a tree is removed following a consultation, people from the wider area are more likely to ask why.”

TfL’s Communications team responds to complaints, Grayham and colleagues offering support on why certain decisions are made. “What anyone in the public sector managing trees would like to get across is that we are not making decisions to make the public’s life worse. We make decisions to benefit them and ensure a legacy of good canopy cover in London stays as long as it can.”

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Climate change, the nature crisis and tragedies such as the death in 2013 of a young girl from Lewisham who suffered a fatal asthma attack and finally recorded in December 2020 as the first death caused by air pollution, all highlight the urgent need for reduced emissions and increased green infrastructure. In addition to the Clean Air Strategy (2019), Highways designers and Project engineers now ask Grayham how they can improve the network and introduce more green assets. “Pollution is caused by vehicles. Changing the types of car people drive and the number of journeys made will have the biggest significance. Within road improvement projects, we consider the best asset type for intercepting particle pollution by where it is positioned. Trees have a high canopy, so we also look at hedgerows and shrub-bed planting.”

Smaller projects harness green ‘roofs’ to encourage biodiversity and ecological connectivity (LU Highgate sidings roof) or incorporate planted containers as part of a Sustainable Urban Drainage (SuDS) system to intercept increased rainwater at train stations. “The South’s corridors of woodlands contain oaks (some 80 to 100 years old), the species that offers the greatest biodiversity value, but climate change affects how trees in specific locations are considered.” Mature London planes on the Victoria Embankment offer little in the way of biodiversity value but much in the way of shade and rainwater interception.


Grayham sees one of his greatest achievements to date as the landscaping along Cycleway 4 (C4) running from Tower Bridge, along Jamaica Road to the Rotherhithe Tunnel roundabout. “We made significant enhancements, bringing in a lot of grass verging and planted areas and 28 new trees. We created the legacy that went with the Cycleway, it just softened it.”

Still sometime before the restrictions of Lockdown 3 are entirely lifted, how does he see the future? “London will continue to grow and evolve, and we will grow and enhance our network. If people to do not return to the network, our business model will have to adjust, and we will have some serious challenges to overcome.”

Tomorrow, Grayham inspects areas of landscaping along the red routes of the A13, managed under a ‘Design, Build, Fund and Operate’ (DBFO) contract. “The road was enhanced via tender and the contractor operates the road on behalf of TfL. I should be onsite most of the day, then drafting-up comments and feedback for the Contracts Manager. I do this 3–4 times a year, surveying and making sure the safety-critical works are done to ensure the network remains well maintained and remains viable.”