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.
Project information
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 x bridges which are being replaced as part of the project. The barrier in the central reservation will be replaced by a new concrete barrier.
Through-junction running will be in place at There are several junctions on this stretch of the M4 which we will be changing so there’s a consistent number of lanes to pass through the junction. This reduces the need to change lane for vehicles staying on the motorway.
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
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
Planning Act 2008 - Development Consent Order Fact Sheet - PDF Size 25KB
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)
Public information exhibition display banners (Spring 2019)
Public information exhibition leaflet (Spring 2019)
M4 junctions 3-12 smart motorway – Public Exhibition Display (July 2018)
M4 junction 3-12 smart motorway – Public Exhibition Leaflet (July 2018)
M4 Junctions 3-12 Smart Motorway – Public Exhibition Poster (2014)
M4 Junctions 3-12 Smart Motorway – Public Exhibition Information (2014)

Traffic information
Information about scheduled roadworks and events on our motorways and major roads.Sign up for updates!
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