M25 junction 28 - Information Portal

Scheme at a glance

The M25 junction 28 plays a huge role in connecting the A12 and the M25, as well as providing access to Brentwood via the A1023. Up to 7,500 vehicles pass through the junction roundabout at peak times.

As it is operating at capacity, vehicles using the junction face congestion and delays, which effects local air quality. Our research shows that traffic is expected to increase in the area by around 30% by 2037, which means that over 9,000 vehicles could be passing through it by this date.

Our improvement scheme will:

• increase capacity and reduce congestion at the junction and on the approaches and exits
• improve safety by redesigning the existing roundabout layout and reducing traffic levels
• provide better connections between the M25 and A12
• reduce annual collision rates through additional capacity
• improve average journey times and reliability for all passing traffic through the junction
• minimise the impact of air and noise pollution in the local area by smoothing the traffic flow
• reduce traffic queuing back onto the M25
• help economic growth in the area by providing improvements to cater for future traffic demands

Our improvements

During main construction we’ll be:

• building a new two-lane loop road, for traffic travelling from the M25 anti-clockwise onto the A12 eastbound (towards Brentwood). This will include the construction of new bridges to take the loop road over or under the other road links, and the Weald Brook; new signage and changes to the landscape
• changing the position of A12 eastbound exit slip road and M25 anti-clockwise entry slip road to allow for the new loop road
• widening the M25 anti-clockwise carriageway to provide more space for traffic leaving for the A12 eastbound

(Visualisation of our improvements)

Length of the scheme

We expect that the main construction work will last around two and a half years, with the scheme open for traffic in summer 2025. The programme has been developed to minimise disruption to all road users and stakeholders.

Road closures

Most of our construction will take place off the road network, with the new loop road and links being almost fully built before we need to do any major work that will impact drivers.

We’ll still need to have some closures. These will be when we link the new roads to the existing network, and while we’re working on the gantries and signage. Any closures will be planned to minimise impact on drivers, with advance notice will be given through our project website and social media.

(Proposed improvements)

Scheme in detail

We’re carrying out a number of improvements to improve the flow of traffic, providing a safer and more integrated network for everyone, and bring real benefits to the drivers who use junction 28 daily.

If we don’t improve the junction, it is predicted that:

• delays will be at least five times greater than they currently are
• average speeds could be reduced by around 25% through the junction
• the local air quality will worsen
• it will constrain development and economic growth in the area
• more widespread disruption following incidents

(Junction 28 as it is now)

Our improvements include:

• a new two-lane loop road with hard shoulder, for traffic travelling from the M25 anti-clockwise onto the A12 eastbound (towards Brentwood). This merges into a single lane to provide a smooth transition between the loop road and A12
• changing the A12 eastbound to allow traffic from the loop road to join into a dedicated lane
• moving the A12 eastbound exit slip road, for traffic using junction 28; and the M25 anti-clockwise entry slip road, for traffic leaving junction 28, to accommodate the new loop road
• widening the M25 anti-clockwise carriageway to provide additional space for traffic leaving to join the A12
• two new road bridges, one carrying the A12 eastbound exit over the loop road, the other to take the loop road over the M25 anti-clockwise entry
• constructing three attenuation ponds, two within the loop road and one to the west. These ponds help us manage surface water from the roads and reduce the risk of flooding
• diverting the Weald Brook and Ingrebourne River to allow construction of the new slip roads
• bridges to take the loop road over the Weald Brook and Ingrebourne River that include specially designed tunnels, known as culverts, which ensure water flows freely under the road, while allowing the movement of wildlife on the banks of the brook
• the installation of new gantries and signage to help everyone move around the junction safely
• landscaping, seeding, planting and improvements to enhance and protect the local wildlife. This includes special fences to keep deer, otters and other wildlife off the road

(Proposed improvements)

How we'll deliver our improvements

We’ll be starting our preparation work in summer 2022, with the main construction starting in October 2022. Our scheme is expected to be open for traffic in summer 2025, with planting and landscaping continuing off network for a short time afterwards.

Since our early consultations, we’ve been busy developing the design and construction plans, and your feedback has helped shape how we’ll be delivering this scheme. 

Most of our construction will take place off the road network, with the new loop road and links being almost fully built before we need to do any major work that will impact drivers. 

We’ll still need to have some closures. These will be when we link the new roads to the existing network, and while we’re working on the gantries and signage.

(Aerial visualisation of our improvements)

Preparation work – from July 2022

The first thing you’ll notice, is us clearing vegetation and a compound being set up to provide welfare and offices for everyone on the site. There will also be teams carrying out surveys, including archaeologists working around the area of the Maylands aerodrome.

There is a gas main running through the site, and we’ll be working with Cadent Gas to get this moved before any construction starts. They’ll be using a specialist machine, called a Tunnel Boring Machine (TBM), to create the new route of the pipe. This is known as a ‘no-dig’ technique and removes the need to dig along the full route of the pipe. Instead, two large holes are dug into the ground at either end of the new pipe route, these are called shafts. The TBM gets lowered into one of these shafts, where it starts its journey below the ground, ending at the other shaft. Once in the end shaft, it gets removed from the ground. 

Main construction – from October 2022

The next phase will see our main construction activities start. This will include earthworks to reshape the landscape and preparing the ground to start building the multiple bridges.

(Construction work)

M25 junction 28 - fly through video

Looking after the environment

To take the surrounding wildlife and environment into account when planning our works, we carried out an Environmental Impact Assessment (EIA). This was completed over a number of years and focuses on how we can help encourage biodiversity, enhance the local watercourses and reduce climate impacts.

An EIA is a tool which is used to assess the potential effects a project can have on the local environment and is in place to ensure we mitigate any potential adverse impacts.

We’ll be minimising our carbon footprint by using recyclable materials, and employing local staff and suppliers wherever possible. To further limit our impact on the environment, we’ll be using biofuels, zero emission welfare units and ensuring that we minimise the miles materials travel both to and from the site.

The scheme has gone through a rigorous carbon assessment, measured by the National Highways Carbon Tool, which is used to calculate the total carbon emissions the project will create.

Wildlife

New large areas of grassland will be created, and we’ll also be enhancing both the River Ingrebourne and Weald Brook, to make it more attractive to mammals such as otters and water voles. These improvements will also see fish such as chubb, gudgeon and stone loach in these watercourses flourish.

Two new attenuation ponds will also be created, to encourage bird and reptile species to the area. These ponds are installed to manage storm and surface water, to help avoid downstream flooding.

As there is a large population of deer in the area, we’ll be providing fencing to ensure that they are kept safely away from roads, to protect both them and drivers.

Within our scheme boundary, we’ve also found great crested newts, a protected species. We’re working with Natural England to provide new habitats for them. 

Archaeology

In order to reduce the impact on local heritage, archaeological assessments shall be carried out prior to our construction works and the Maylands aerodrome will be a key feature of this.

Maylands has significant importance to the British aviation history, as it was one of the first sites to offer package holidays in 1930s and had world renowned pilots Amy Johnson and Jim Mollison fly out of the airfield. We will be inviting local heritage groups to join us when excavating the area.