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

M3 junctions 9 to 14: smart motorway

Latest updates

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.

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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 lane, adding 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’.