M25 junction 23

Improving junction 23 of the M25 by increasing capacity.

Start date August 2019
End date May 2021
Cost £7.5 million

Latest updates

  • 07 May 2021

    Scheme completion planned for end of May

    With all major works now complete, we’ve been able to remove the traffic management from around the junction.

    During May, there will be some additional overnight closures of the southeast quadrant of the roundabout and the A1 southbound entry slip road. This is to complete outstanding electrical work which had to be rescheduled.

    Once the electrical work is completed, there will be a commissioning phase, which will enable the new traffic signals to be optimised. This will ensure the new improvements are working to their expected potential

  • 12 April 2021

    Closures this week as scheme nearing completion

    During March, we completed work to resurface and renew road markings, install new street lighting and road signs.

    There is now a focus on completing our works at Bignells Corner, where we’re constructing an additional lane to increase vehicle capacity, upgrading the traffic signals to help improve traffic flow, and building a new pedestrian footway from the BP service station to the existing footway next to the roundabout.

    The northeast quarter of the roundabout, between the A1(M) northbound entry slip road and the M25 anti-clockwise exit slip road, including the A1(M) southbound exit slip road, Bignells Corner inbound and outbound carriageways and the M25 clockwise entry slip road, will be closed overnight between 10pm and 5am, from Monday 12 April for seven nights.

    The following clearly signed diversions will be in place:

    • Traffic from A1(M) southbound for the M25 anti-clockwise will be diverted via the A1 southbound to Stirling Corner and return.
    • Traffic from A1(M) southbound for the M25 clockwise traffic will be diverted via the A1 southbound to Stirling Corner roundabout, north on the A1, to M25 junction 22 and return.
    • Non-motorway users will be diverted via Bignells Corner, Swanland Road, St Albans Road northbound, Cecil Road, Mutton Lane eastbound, Barnet Road southbound, Dancers Hill Road westbound and St Albans Road northbound.

    The below road closures will enable our teams to safely progress work on street lighting, traffic signals, signage, and carriageway surfacing and lining.

    In addition, the exit from the South Mimms Welcome Break Services and Lorry Park will be temporarily closed between 1am and 4am on the morning of Thursday 15 April, as part of the work required to upgrade the traffic signals at Bignells Corner.

  • 11 March 2021

    Bignells Corner update

    Since the beginning of 2021, we have completed work to reinstate a new drainage channel, install new kerbs and resurface sections of the roundabout carriageway. We have also finished installing new utility channels and street lighting at Bignells Corner.

    Current activities are being done whilst closing lane two on the inbound carriageway, and lane one on the outbound carriageway overnight.

    Continued periods of cold and wet weather throughout January and February meant we were unable to carry out some of our planned resurfacing work of Bignells Corner.

    To complete this work, we will be closing the road over seven nights starting from Monday 8 March (between 10pm and 5am). A clearly signed diversion will be in place via junction 22 of the M25 and the B556 to Bignells Corner.

    If you would like to subscribe to our monthly newsletter, please contact JIP@CONNECTPLUSM25.CO.UK

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  • 13 November 2020

    Overall works over 80% complete

    Works around the junction have recently seen the removal of the temporary safety barriers on the M25 anti-clockwise exit slip road returning to three narrow traffic lanes. This will help increase capacity when approaching the roundabout. Sheet piling works on the A1 southbound entry slip offside verge are now also complete.

    Works at Bignells Corner have currently been suspended for the safety of the travelling public and our workforce, due to an increase in non-compliance with traffic management. Our teams are currently working to find the safest solution to completing the works within this area as efficiently as possible, and plan to continue works in this location starting in late November.

    Our works over the coming month look to complete the widening works on the A1 southbound entry slip road, recommence our works at Bignells corner and prepare for planned resurfacing works around the junction.

    If you could like to subscribe to our monthly newsletter please email us: JIP@CONNECTPLUSM25.CO.UK

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  • 26 May 2020

    Works at Bignells Corner gets under way

    We’re bringing our planned works at Bignells Corner forward and will be carrying out some of these shifts between 8am and 5pm until June. To allow us to undertake these works safely, the full closure of the outbound dual carriageway to the junction 23 circulatory will be required. At least one traffic lane will be re-opened at the end of each shift. Lanes may remain closed outside of working hours for the safety of road users.

    Traffic counts will be undertaken daily and should traffic levels start to increase towards normal levels, works will be reverted to overnight shifts.

    If you could like to subscribe to our monthly newsletter please contact JIP@CONNECTPLUSM25.CO.UK

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    Coronavirus (Covid-19)

    Our current priority is to play our part in keeping the country safe, whilst supporting the movement of essential supplies, services and people who cannot work from home. We are following the government’s policy, which advises that construction activity should continue where it can be done safely. All our sites have strict safeguarding measures, in line with Public Health England guidance, to prevent the spread of Covid-19 and protect workers and the public.

  • 12 May 2020

    Work completed so far

    Works completed or underway since the start of the scheme in August 2019.

    A1 southbound nearside:

    • Sheet piled retaining wall has been completed
    • Drainage works have been completed
    • Ductwork for new lighting has been installed
    • Surface water channel has been completed
    • Pavement works are currently underway

    A1 southbound offside:

    Vegetation clearance has been completed

    Gyratory opposite M25 anti-clockwise exit slip road:

    • Drainage has been completed
    • Ductwork for signals has been completed
    • Works are currently underway on new signage and landscaping

    M25 anti-clockwise exit slip road:

    • Sheet piled retaining wall and reinforced concrete capping beam have been completed
    • Drainage has been completed
    • Street lighting and traffic signal ducting has been completed
    • Pavement construction is currently underway

    Bignells Corner:

    • Site clearance has been completed
    • Temporary street lighting has been installed
    • Earthworks for pavement on nearside and offside is currently underway

Project information


Work will see widening of the A1 southbound merge slip road to provide a two-lane entry to the A1 south and a new footway for pedestrians from the BP service station to the existing footway adjacent to the roundabout. 

The scheme incudes an upgrade to the traffic signal timings to improve traffic flow through the junction. There will be a new lane at the Bignells Corner exit from South Mimms services with widening of the M25 westbound exit slip road to accommodate an additional lane on the approach to the junction to reduce congestion. 

The M25 junction 23 is controlled by traffic signals, and is where the M25, A1, A1(M) and A1081 meet. Junction 23 is operating over its design capacity, which leads to congestion, queuing traffic and journey delays during peak hours. The junction 23 scheme also provides for safety improvements within its design as well as a more free-flowing network with reduced congestion and more reliable journey times. 


Traffic information

Information about scheduled roadworks and events on our motorways and major roads.

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