M3 junctions 9 to 14: smart motorway

We’re upgrading the M3 between junction 9 (Winchester/A34 interchange) and junction 14 (M27 Southampton interchange) to an all-lane running smart motorway. The scheme will link to the forthcoming smart motorway on the M27.

Start date Started
End date 2023-24
Cost £139 million

Latest updates

  • 30 April 2021

    Preparation for starting work this summer

    We’ve been clearing vegetation along the side of the M3, undertaking surveys and diverting cables in preparation for upgrading the motorway.

    Later this year we’ll be installing narrow lanes in both directions between junctions 9 and 14, and the hard shoulder will be used as a running lane. This will provide a safe working area in the central reservation, whilst keeping three lanes open during the daytime.

    To prepare the hard shoulder for this, work to strengthen the verges is expected to start early May 2021.

    This means that there will be occasional overnight closures of the motorway, lane closures or closures of entry and exit slip roads. Where the motorway or a slip road is closed, a signed diversion will be in place. We have scheduled these closures for weeknights to minimise disruption.

    Please sign up to our email alerts to keep updated about the scheme and to learn more about the motorway upgrade.

    Timeline of works

    Our key milestones are:

    • Spring/Summer 2021 – On-going site clearance and preparatory work
    • Spring/Summer 2021 – CCTV cameras installed
    • Summer 2021 – Installation of temporary traffic management (narrow lanes and a 50mph speed limit enforced by average speed cameras)
    • Late Summer/early Autumn 2021 – Work to upgrade the M3 will start in the central reservation

    Please note these are indicative timeframes

  • 23 February 2021

    Preparatory works ongoing

    We’re currently clearing some of the vegetation along the side of the road where we’ll be working later this year.

    We’re also continuing to survey the route in preparation for the motorway being upgraded.

  • 23 January 2020

    Public consultation results

    Last year we consulted on proposals to implement variable mandatory speed limits on the M3 between junctions 9 and 14. You can now read the results of that consultation in the report.

  • 20 January 2020

    Timeline of works

    From January 2020 we’ll occasionally close one lane of the motorway so we can safely clear vegetation and finish our survey work.

    Our key milestones are:

    • Winter/spring 2020 – Start site clearance and preparatory work
    • 2020-22 – Start building the new smart motorway

  • 06 November 2019

    Preparatory works

    We’ll be getting the M3 ready to become a smart motorway early next year. This will involve clearing vegetation and repairing the hard shoulder.

    We carried out four public information events in September 2019 to gather feedback on our design and inform people about smart motorways. Our brochure and the information banners we displayed are still available for you to view in the project media files section.

    Please sign up to our email alerts to keep updated about the scheme and planned public events, and to learn more about the smart motorways programme.

Project information


The M3 motorway is a key part of the strategic road network and provides a vital economic link from the Midlands (via the A34) and London to the major ports of Southampton and Portsmouth on the south coast (via the M27).  

By 2036 this 10-mile stretch of the M3 is forecast to carry at least 20,000 more vehicles a day compared to 2015. We’re converting it into a smart motorway, so it has capacity for these forecast levels of traffic. 

It involves changing the hard shoulder into a running laneadding more signs, deploying variable speed limits from overhead gantries and building emergency refuge areas.

Between junction 9 (Winchester) to 13 (Eastleigh), the M3 will operate four-lanes in each direction. This is known as ‘all-lane running’ and involves the existing hard shoulder being converted into an additional lane for vehicles.  

Road users driving northbound and joining the M3 at junction 14 where the roads converge from the M27 eastbound, westbound and from Southampton will see the M3 operate four lanes and a hard shoulder up to junction 13.  

For road users driving southbound from junction 13 (Eastleigh) towards junction 14 (Southampton), the road will transition from four lanes with no hard should shoulder and then split into two separate roads to link to the M27 East and West. 

The section of the M3 linking to the M27 eastbound will feature two lanes and a hard shoulder. The section of the M3 linking to the M27 westbound will comprise three lanes with no hard shoulder. The road layout into Southampton will remain as it is now.  

The section from after junction 13 (Eastleigh) to junction 14 (Southampton) is a variation of smart motorway known as a ‘controlled motorway’.


Traffic information

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

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