M4 junctions 3-12: smart motorway

We’re improving the M4 between junction 3 at Hayes and junction 12 at Theale by upgrading it to a smart motorway. This means there will be an additional lane for traffic which will increase capacity and reduce congestion, more technology on the road to smooth traffic flows and manage incidents and more reliable journey times.

Start date 2018
End date 2022
Cost £848 million

Latest updates

  • 13 October 2021

    Update and planned weekend closures for October 2021

    During early October, the cones are being removed from lane one between junctions 8/9 and 12. Four full width lanes will be open to traffic at a temporary speed limit of 60mph. The temporary speed limit will remain in place until later this year while the automated elements of the new technology are calibrated.

    During this time, while the technology is monitored, the construction CCTV and free recovery will remain in place and more traffic officer patrols will be present. Towards the end of the year, the upgraded motorway will be fully opened at 70mph and all the inter-related features working together.

    Planned weekend closures for October 2021

    16 October – 18 October 2021 – weekend closure between junctions 3 and 4b

    The M4 will be closed in both directions over the weekend of 16 October – 18 October 2021 between Junctions 3 (Hayes) and 4b (M25 interchange). The closure will start after 4am Saturday 16 October and the motorway will reopen by 6am on Monday 18 October.

    22 October – 25 October 2021 – OVERNIGHT ONLY weekend closure between junctions 4b and 5

    The M4 will be closed in both directions overnight only during the weekend of 22 October – 25 October 2021 between junctions 4b (M25) and 5 (Langley). The closure will start after 8pm Friday 22 October and the motorway will reopen by 6am each morning.

    29 October1 November 2021 – OVERNIGHT ONLY weekend closure between junctions 6 and 8/9

    The M4 will be closed in both directions overnight only during the weekend of 29 October – 1 November 2021 between Junctions 6 (Slough) and 8/9 (Maidenhead). The closure will start after 8pm Friday 29 October and the motorway will reopen by 6am each morning.

    Please check before you travel.

    Our October 2021 scheme newsletter gives more information about the opening of junction 8/9 to 12 to 60mph across four full lanes. There will be further updates about closures on this page. 

  • 27 August 2021

    Planned weekend closures for September 2021

    3 September – 6 September 2021 – full weekend closure between junctions 3 and 4b

    The M4 will be closed in both directions over the weekend of 3 September – 6 September 2021 between Junctions 3 (Hayes) and 4b (M25 interchange). The closure will start after 8pm Friday 3 September and the motorway will reopen by 6am on Monday 6 September.

    10 September – 13 September 2021 – full weekend closure between junctions 3 and 4b

    The M4 will be closed in both directions over the weekend of 10 September – 13 September 2021 between Junctions 3 (Hayes) and 4b (M25 interchange). The closure will start after 8pm Friday 10 September and the motorway will reopen by 6am on Monday 13 September.

    17 September – 20 September 2021 – full weekend closure between junctions 5 and 6

    The M4 will be closed in both directions over the weekend of 17 September – 20 September 2021 Junctions 5 (Langley) and 6 (Slough). The closure will start after 8pm Friday 17 September and the motorway will reopen by 6am on Monday 20 September.

    24 September – 27 September 2021 – full weekend closure between junctions 6 and 8/9

    The M4 will be closed in both directions over the weekend of 24 September – 27 September 2021 between Junctions 6 (Slough) and 8/9 (Maidenhead). The closure will start after 8pm Friday 24 September and the motorway will reopen by 6am on Monday 27 September. 

    Our August 2021 scheme newsletter gives more information about full weekend closures of the M4 planned for 2021. There will be further updates on this page. Please check before you travel. 

  • 16 June 2020

    Project reaches halfway point

    In June 2020 the project hit the halfway point with the work to extend the New Thames Bridge at Bray that carries the M4 over the river. This bridge - started in 1937, delayed by World War II, and completed as part of the new M4 motorway that opened in 1961 – is being widened on the north side by 8 metres to accommodate the extra lanes required for the new smart motorway.

    We are continuing our steady progress on the western section between junctions 8 and 9 to junction 12 which started in July 2018. We expect to finish most of the work on this section by the latter part of 2020, before opening it as a smart motorway during 2021. The eastern section is more complex due to a significant amount of bridge work and will open in 2022.

    We are following Government policy which is that construction activity should continue where it can be done safely. All our sites have strict safeguarding measures to prevent the spread of COVID-19 and none of our sites are open to the public. With traffic volumes on our roads still lower than usual, we are continuing to work before traffic flows eventually return to normal. We plan our work carefully in order to minimise travel disruption.

Project information

Overview

Once our work is completed this stretch of the M4 will use the latest technology to monitor traffic flow and set speed limits. This will help keep traffic moving smoothly, instead of continually stopping and starting. 

Between junctions 3 and 12 the hard shoulder will be converted to a traffic lane, so there will be four lanes available for use by road users. Between junctions 4 and 4b, there will be five lanes. There will also be five lanes on the eastbound approach to Junction 4b. 

Where a hard shoulder does not currently exist, the motorway will be adapted to create a minimum of four lanes, including under the 11 bridges which are being replaced as part of the project. The barrier in the central reservation will be replaced by a new concrete barrier. 

The M4 is the main strategic route between London, the West of England and Wales. It connects people, communities and businesses, carrying on average 130,000 vehicles per day. 

The changes we’re making will 

  • reduce congestion 
  • smooth the flow of traffic to improve journey times 
  • make journeys more reliable 
  • support economic growth within the region, by providing much needed capacity on the motorway  
  • continue to deliver a high level of safety performance on the network using smart motorway techniques and minimise environmental impacts of the scheme

The DCO process was established by the Planning Act 2008 and is used for certain large and complex schemes (including highway improvements) that have been designated as a Nationally Significant Infrastructure Project (NSIP) by the Government.

The benefits of the DCO process include extensive pre-application consultation, detailed analysis, including a full Environmental Impact Assessment, and examination by an independent inspector before the final decision is made.

Development Consent Order – requirements register

We made a commitment to publish and update a register listing the requirements to be completed as part of the Development Consent Order (specified under the Register of Requirements in Schedule 2). This sets out:

  • each requirement
  • whether the requirement needs approval by the Secretary of State (or other duty holder)
  • whether any approval has been applied for or given

All of the DCO requirements needed to start work were discharged in summer 2018.

Documents

Newsletters

M4 junctions 3 to 12 smart motorway - Newsletter October 2021
M4 junctions 3 to 12 smart motorway - Newsletter August 2021
M4 junctions 3 to 12 smart motorway - Newsletter July 2021
M4 junctions 3 to 12 smart motorway - Newsletter June 2021
M4 junctions 3 to 12 smart motorway - Newsletter May 2021
M4 junctions 3 to 12 smart motorway - Newsletter April 2021
M4 junctions 3 to 12 smart motorway - Newsletter March 2021
M4 junctions 3 to 12 smart motorway - Newsletter February 2021
M4 junctions 3 to 12 smart motorway - Newsletter January 2021
M4 junctions 3 to 12 smart motorway - Newsletter December 2020
M4 junctions 3 to 12 smart motorway - Newsletter November 2020
M4 junctions 3 to 12 smart motorway - Newsletter October 2020
M4 junctions 3 to 12 smart motorway - Newsletter - September 2020
M4 Junctions 3 to 12 smart motorway - Newsletter - August 2020
M4 junctions 3 to 12 smart motorway - Newsletter July 2020
M4 junctions 3 to 12 smart motorway - Newsletter June 2020
M4 junctions 3 to 12 smart motorway - Newsletter May 2020
M4 junctions 3 to 12 smart motorway - Newsletter April 2020
M4 junctions 3 to 12 smart motorway - Newsletter March 2020
M4 junctions 3 to 12 smart motorway - Newsletter February 2020
M4 Junctions 3 to 12 Smart Motorway - Newsletter - January 2020
M4 Junctions 3 to 12 Smart Motorway - Newsletter - December 2019
M4 Junctions 3 to 12 Smart Motorway - Newsletter - November 2019
M4 Junctions 3 to 12 Smart Motorway - Newsletter - October 2019
M4 Junctions 3 to 12 Smart Motorway - Newsletter - September 2019
M4 Junctions 3 to 12 smart Motorway - Newsletter - Summer 2019
M4 Junctions 3 to 12 Smart Motorway - Newsletter - June 2019
M4 Junctions 3 to 12 Smart Motorway - Newsletter - May 2019
M4 Junctions 3 to 12 Smart Motorway - Newsletter - April 2019
M4 Junctions 3 to 12 Smart Motorway - Newsletter - March 2019
M4 Junctions 3 to 12 Smart Motorway - Newsletter - February 2019
M4 Junctions 3 to 12 Smart Motorway - Newsletter - January 2019
M4 Junctions 3 to 12 Smart Motorway - Newsletter - December 2018
M4 Junctions 3 to 12 Smart Motorway - Newsletter - November 2018
M4 Junctions 3 to 12 Smart Motorway - Newsletter - October 2018
M4 Junctions 3 to 12 Smart Motorway - Newsletter - September 2018
M4 Junctions 3 to 12 Smart Motorway - Newsletter - July 2018

Traffic information

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

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