Have your say
We've introduced a new engagement tool where you can give your views on the project. Please click on the map below to add your comments about specific parts of the route.
Activity is now underway all along the route including:
- preparatory work on structures and verges
- installing new technology
- building the carriageway.
We are making excellent progress on the western section between junctions 8 and 9 to 12 and have recently started work on the eastern part of the scheme. We will start the first bridge replacements in autumn. Read our summer newsletter for more information.
From spring 2022, the completed smart motorway will increase capacity, reduce congestion and deliver more reliable journeys.
In Autumn 2019, one of the most complex phases of the project will get underway with the start of bridge replacement work between junctions 8/9 (Maidenhead) and 4b (the M25). Preparatory work has started on many of the bridges on this stretch, but major work will start this autumn on:Recreation Ground overbridge
This is primarily a pedestrian and cycle route linking Datchet to Upton Court Park.It will be demolished in late September. The new bridge will be in place by Summer 2020. Public access to the bridge will be removed from 9th September 2019 and we expect this to be reinstated as soon as possible after the new bridge is complete in late Summer 2020.Marsh Lane overbridge (just west of the Jubilee River near Dorney)
This will be demolished in mid-November. Local traffic will be diverted via Lake End Road overbridge until the new Marsh Lane bridge is complete towards the end of 2020.Monkey Island Lane overbridge (just west of the River Thames also near Dorney)
Preparation work is well underway here. We will lift the new bridge beams in mid-November. The existing bridge will remain in place until the replacement is ready.Huntercombe Spur overbridge at junction 7
This will be demolished in late November. A temporary overbridge will be installed in advance and will be in place throughout the construction process so there will be minimal interruption to traffic on the junction.
For this work we have to close the motorway for entire weekends because we wouldnâ€™t be able to complete the necessary demolition and construction closing the road just at night.
The M4 is scheduled to be closed in both directions between junctions 5 and 6 the last weekend of September. These dates are subject to change so check the planned roadworks feed for further details. The closure information should be available around 2 weeks before the closures are due to start.
|March 2008||Advanced motorway signalling and traffic management feasibility study identified this motorway link as a priority for additional capacity|
|2009||Department for Transport announces a programme of smart motorways, including this scheme|
|2010||Scheme development commenced|
|2013||Roads Minister announces funding for this scheme|
|November 2014 to December 2015||Pre-application consultation|
|January to February 2015||Speed limit consultation|
|30 March 2015||Development Consent Order submitted|
|27 April 2015||Planning application accepted for examination|
|July 2015||CH2M and Arcadis appointed to develop detailed scheme design|
|July 2015||Balfour Beatty Vinci Joint Venture appointed to develop construction methodology and programme|
|2 September 2016||Secretary of State decision|
|15 October 2016||High Court Challenge period ended|
|March 2017||Start of preparation works|
|July 2018||Public information exhibitions|
|July 2018||Start of main works|
|15 July 2019 to 14 August 2019||Statutory Instrument Consultation|
|Spring 2022||Smart Motorway complete and operating|
Indicative timings of the works
This is the longest smart motorway project in England to date (51km, 32 miles). We have carefully planned our work to minimise disruption to our drivers and communities.
We started main works between junction 8/9 and 10 in July 2018 and have since progressed our traffic management west towards junction 12, and east towards junction 7. In tandem we have started enabling work on several bridges between junction 8/9 and junction 7. The more complex section of the scheme, progressing east towards junction 3, is now getting underway. Work on the carriageway between junctions 3 and 4b starts in September 2019.
Much of the M4 was originally built as a 2-lane dual carriageway and has been upgraded several times over the years. 11 bridges over the motorway need to be replaced to make room for a new lane where there is no existing hard shoulder.
To limit local disruption, most new bridges will be built next to the existing ones, before the old one is demolished or a temporary bridge will be installed. However, where there is not enough space for this, some bridges will be demolished first, then a new bridge built in the same place.
Where the motorway passes over, for example, the River Thames at Bray, we will need to widen structures to support the new smart motorway.
Wherever possible, noisier works will be undertaken during daytime hours to reduce disturbance. There will be temporary closures of the carriageway and slip roads at night on some occasions.
In these instances, the closure will be advertised, and advance warning signs and clearly signed diversions will be put in place. You can use the Roadworks section below to find information about roadworks as the scheme progresses.
The construction of the scheme is governed by the Construction, Design and Management Regulations, and we are a member of the Considerate Constructors scheme which helps ensure that we are a good and responsible neighbour.
Why we need this scheme
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 and is prone to congestion.
Highways England will be improving the M4 between junction 3 at Hayes and junction 12 at Theale by upgrading it to a smart motorway which will provide much needed capacity and support the economy and facilitate economic growth within the region. This means there will be:
- an additional lane for traffic increasing capacity to reduce congestion
- more technology on the road to smooth flows and manage incidents
- more reliable journeys
The scheme in detail
This scheme will use the latest technology to improve journeys by monitoring traffic flow and setting speed limits accordingly. This helps to keep traffic moving smoothly, instead of continually stopping and starting.
Information about road conditions and speed limits will be displayed to drivers on electronic road signs.
Key changes to the motorway
All Lane Running: between junctions 3 and 12 the hard shoulder will be converted to a traffic lane, so that there are 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 the replacement of bridges. The barrier in the central reservation will be replaced by a new concrete barrier.
Through junction running: This enables a consistent number of lanes to pass through the junction, reducing the need to change lane for vehicles staying on the motorway. Through-junction running will be in place at several junctions on the smart motorway where it is assessed to be appropriate.
To accommodate the new smart motorway 11 bridges carrying local traffic over the motorway will need demolition and replacement.
Where the motorway passes over, for example, the River Thames at Bray, we will need to widen bridges to support the new smart motorway.
Several subways, including at Sipson, and several culverts that run under the motorway will also need work in order to accommodate the upgrade.
Emergency areas (EAs): there will be new high visibility Emergency Areas between junctions 3 and 12. Places of relative safety will be every 1.12 miles on average and no more than 1.6 miles apart. If you are driving at 60mph you will pass one approximately once every 90 seconds.
AimsThe objectives of the proposed scheme are to:
- reduce congestion
- smooth the flow of traffic to improve journey times
- make journeys more reliable
- support the economy and facilitate 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
Development Consent Order (DCO)
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 â€“ 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.
Wherever possible, noisier works will be undertaken during daytime hours to reduce disturbance.
There will be temporary closures of the carriageway and slip roads at night on some occasions. In these instances, the closure will be advertised, and advance warning signs and clearly signed diversions will be put in place. You can use the Roadworks section below to find information about roadworks as the scheme progresses.
The construction of the scheme is governed by the Construction, Design and Management Regulations, and we're a member of the Considerate Constructors scheme which will help ensure that we're a good and responsible neighbour.
As part of the DCO planning process, a full Environmental Impact Assessment was carried out and has been used to inform the design of the project. This included assessments and design of mitigation where needed for:
- air quality
- cultural heritage
- ecology and nature conservation
- geology and soils
- noise and vibration
- effects on all travellers
- community and private assets
- road drainage and the water environment
During the examination of the application, further environmental protections were requested and planning requirements attached to the consent.
Project media files and documents
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
Public information exhibition leaflet (Spring 2019)
M4 junctions 3-12 smart motorway â€“ Public Exhibition Display (July 2018)
M4 junction 3-12 smart motorway â€“ Public Exhibition Leaflet (July 2018)
M4 Junctions 3-12 Smart Motorway â€“ Public Exhibition Poster (2014)
M4 Junctions 3-12 Smart Motorway â€“ Public Exhibition Information (2014)
M4 Junctions 3-12 Managed Motorway - Business Case
M4 Junctions 3-12 Smart Motorway - Planning Inspectorate Introductory Meeting (2014)
Section 48 - Planning Act Notice (2014) - PDF Size 167KB
M4 Junctions 3 to 12 Smart Motorway (1 of 2) Red line drawings for scoping (2014)
M4 Junctions 3 to 12 Smart Motorway (2 of 2) Red line drawings for scoping (2014)
Roadworks and Events for England
The latest incident information for England's motorway and trunk routes provided by Highways England
Breaking News: Traffic Information
The latest current breaking news items for England's motorway network