M3 Junctions 2-4a: Smart Motorway

Project status:   Current

Start date:   Autumn 2014
End date:  Main works: winter 2016

Type:   Major Scheme
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Major Scheme

Part of our programme of improvements (value >10m)

Cost:  Between £138 million and £198 million


A new approach to delivering road works

This project is taking part in a trial to make road works simpler and clearer for peo­ple to drive through. 

For more information please visit the traffic information page.

M3 Junctions 2 to 4a Latest

In the November 2011 autumn statement, the Chancellor announced that the M3 Junction 2 to 4a would be upgraded to a smart motorway as one of six growth schemes which would be prepared for construction before 2015.

The main construction works are being delivered by Balfour Beatty and commenced in January 2015 for 26 months.

Throughout the construction period we will ensure the safety of the public and workforce; minimise the impact of work on the local communities; minimise delays to road users and do all we can to protect the local environment.

For further information please refer to the scheme newsletter which can be found on the Publications tab.

Traffic Management

We operate 24 hours, 7 days a week CCTV cameras throughout the works. Any incidents, accidents or breakdowns occurring within the roadworks are monitored and vehicles are recovered free of charge as quickly as possible by our dedicated on-site vehicle recovery service. Drivers and their passengers are taken to our customer care centre where they can wait in safety and comfort whilst making arrangements for their onward journey.

We will:

  • maintain three lanes of traffic both west and eastbound
  • limit full closures to the minimum
  • manage full closures to avoid local events

In order to carry out the construction works safely, a speed limit of 50mph will be in place throughout the works. This is for the safety of the public and workforce and will be monitored by a speed enforcement camera system. This project team will work hard to reduce the impact on motorists, local residents and businesses. We will advise local residents and businesses in advance of any planned changes and road closures and respond in a timely manner to all concerns.

You can help by:

  • driving safely through roadworks
  • keeping to the speed limit, it is there for everyone’s safety
  • getting into the correct lane in good time
  • not switching lanes
  • concentrating on the road ahead, not the roadworks
  • keeping a safe distance from the vehicle in front

Further Traffic Management information including closures can be found on the Journey Impact tab.

Ground Investigation Surveys

Ground surveys carried out ahead of the scheme works indicated that ground conditions on the M3 made it likely that we would discover small underground cavities or voids. Some of the voids that we have discovered prior to construction were larger than expected – in particular two that were found on the hard shoulder near junction 2 late last year.

From Tuesday 31 March, and for the following 12 nights, we will be carrying out additional investigative work in the verge alongside the carriageway. The aim of these works is to drill exploratory holes in areas we suspect that there may be a void or cavity. The last hole will be drilled at 2am, which means we should be able to fill any void, should it be necessary, before the lane closure is due to come off at 5.30am. However, should a void be found which requires filling over a longer period of time, we may have to keep that lane closed off from running traffic until the following night.

It is not anticipated that we will find any further voids, however we are keen to avoid any unnecessary disruption while we carry out work to upgrade the M3, which might be caused should we not undertake these inspections.


What is happening?

We propose to improve the M3 by making it a "smart motorway" between junctions 2 and 4a (13.4 miles / 21.6km). Smart motorways help relieve congestion by using technology to control traffic flows and assist in the management of incidents and providing information to road users. They deliver these benefits at a significantly lower cost than conventional motorway widening and with less impact on the environment during construction. This will be achieved by converting the existing hard shoulder to a permanent running lane. Find out more about Smart Motorways.

We are aware of concerns being raised by residents living close to the project route regarding possible noise and visual intrusion issues. These concerns have been noted and are being considered as part of the project's ongoing development and design.

When and where is this happening?

In the November 2011 autumn statement, the Chancellor announced that the M3 junction’s 2-4a smart motorway (formerly known as managed motorway) scheme would be prepared for construction before 2015. The 2012 Budget confirmed the start of work for this scheme to be in financial year 2013/14, subject to the outcome of statutory processes. Since then, the Prime Minister announced that this scheme would be one of four schemes to be included in a pilot to significantly reduce the delivery time of road schemes.

Why is this happening and what will it cost?

The M3 between J2 and J4a experiences high traffic flows during both peak periods (am and pm) and has a higher than average accident rate.

The March 2008 ' Advanced motorway signalling and traffic management feasibility study' identified this motorway link as a priority for the provision of additional capacity and ministers agreed that smart motorways, as an alternative to widening, should be investigated.

The estimated cost of this scheme is in the range of £138 million and £198 million.

How will the scheme be carried out?

Smart motorway schemes have been in operation for a few years on the strategic network e.g.M42 and the concept together with their benefits is better understood. Further improvements have been made to the original concept and these developments include permanently converting the hard should to a running lane and developing the design so that schemes will have:

  • Fewer overhead gantries which span the whole motorway
  • Fewer signals over each lane and more verge mounting signing
  • Comprehensive CCTV camera coverage – although there will no longer be the need for dedicated cameras to open and close the hard shoulder.

A number of cameras, information signs and signals on gantries will be installed as part of the improvement scheme. As the scheme design progresses we will provide more information on the location of these features.

The feasibility study for the M3 identified a single option which will allow vehicles run on the Hard Shoulder on the M3 J2-J4a without Through Junction Running (TJR). This option is being further developed to ensure best Value for Money and minimal environmental impact can be achieved. The design is being further developed to ensure best Value for Money with minimal environmental impact.

The scheme will comprise the following elements:

  • MIDAS Queue protection technology
  • CCTV coverage
  • MS4 information signs
  • Lane specific speed signals at certain locations
  • Variable speed limits
  • Speed enforcement
  • Permanent hard shoulder usage as a running lane
  • Emergency refuge areas with emergency telephones
  • Low noise road surfacing (at locations where resurfacing is likely to be required as part of the project)

What are the benefits?

This project will:

  • relieve congestion
  • smooth the flow of the traffic
  • improving safety and reduce serious accidents
  • improve journey times
  • provide better information to road users

These benefits will also support economic development in the region.

We already have evidence of the benefits that a smart motorway scheme can bring. The first smart motorway scheme opened to traffic on the M42 motorway in 2006. Recent analysis of the data gathered since opening has found that journey time reliability improved by 22 per cent and reduced emissions by up to 10 per cent due to traffic flowing more smoothly. In addition, personal injury accidents have reduced by more than half (55.7%) since hard shoulder running was introduced. There was also an overall reduction in the severity of accidents with zero fatalities and fewer seriously injured.

How do I find out more information ?

More information will be posted on this project page as it becomes available. You can subscribe to be alerted when updates are made.

If you have any queries about this project you should contact the Highways Agency Information Line by emailing ha_​info@​highways.​gsi.​gov.​uk or calling 0300 123 5000.

Details of scheduled roadworks are provided to help you plan your journey. Please note that works are weather- and resource- dependent and may need to be cancelled at short notice. This information is not updated in real time so please check Traffic England for current traffic conditions. Diversion timings are approximate and act as a guide only.

Will there be roadworks?

Yes, roadworks will be needed.

Please note that this project is taking part in a trial to make road works simpler and clearer for peo­ple to drive through.

For more information please visit our traffic information webpage.

Road Works

DateDurationDetailsAllow an Extra
Saturday 25th July 20159pm – 5amM3 northbound junction 4a to 3 including junctions 4a and 4 entry slip roads closed
Monday 27th July 201510pm – 5.30amM3 Northbound Junction 3 to 2 including junctions 3 entry slip
Tuesday 28st July 201510pm – 5.30amM3 Northbound Junction 3 to 2 including junctions 3 entry slip
Wednesday 29th July 201510pm – 5.30amM3 Northbound Junction 3 to 2 including junctions 3 entry slip
Thursday 30th July 20159pm – 5.30amM3 Northbound Junction 4a to 3 including junctions 4a and 4 entry slip roads closed
Friday 31st July 201510pm – 6amM3 Northbound Junction 4a to 3 including junctions 4a and 4 entry slip roads closed
Saturday 1st August 20159pm – 5amM3 Northbound Junction 4a to 3 including junctions 4a and 4 entry slip roads closed

How will you manage traffic?

We will continue to provide 3 lanes of traffic in both directions utilising both narrow lanes and a contraflow where appropriate.

Will there be diversions?

We will endeavour to keep full closures to a minimum where we are able. However, some closures will be required at night with clearly signed diversion routes in place.

The diversions are:

M3 Northbound Jct 4a to 3 full carriageway closure including Jct 4a and 4 entry slips closed:

M3 Northbound J4a to A327 to A30 to M3 J3.

M3 Northbound J4 to A331 to A30 to M3 J3.


Business Case

M3 Junctions 2-4a Managed Motorway Business Case
Business Case - Information correct as at December 2010


M3 Junctions 2-4a Smart Motorway Environmental Assessment Report
The purpose of the Environmental Assessment Report (EAR) is to assess whether or not significant environmental effects would be likely to occur as a result of construction and/or operation of the Scheme.


M3 J2-4a Public Information Exhibition - presentation
M3 J2-4a Public Information Exhibition - presentation



M3 Junction 2 - 4a newsletter
M3 Junctions 2-4a newsletter


M1 Junctions 28 to 35a Air Quality Mitigation Summary of Consultation Responses
Responses to the consultation on proposal to introduce a maximum mandatory 60mph speed limit on the M1 between junction 28 and 35a.
M3 Junctions 2-4a Managed Motorway Statutory Instrument Consultation Report
M3 Junctions 2-4a Managed Motorway - Response to the Consultation Report - September 2013