The Smart Motorway schemes

M3 smart motorway upgrade

National Highways (formerly Highways England) are 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 soon to be completed smart motorway on the M27 (jcts 4 to 11).

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. Converting it into a smart motorway will give it the capacity to carry these forecast levels of traffic.

The works, starting in late summer 2021, involve changing the hard shoulder into a running lane, adding more signs, deploying variable speed limits from overhead gantries and building emergency refuge areas.

There is an overview of the expected works on the Highways England website and you can keep up to date with the smart motorway works by subscribing to the Highways England newsletter.

M27 smart motorway upgrade

The M27 smart motorway scheme stretches from junction 4 (M3 Interchange) to junction 11 (Fareham), and will directly connect to the M3 junction 9 (Winchester / A34 Interchange) to junction 14 (M27) smart motorway scheme. The scheme is 24km (15 miles), and all links on the M27 between junction 4 to 11 will be upgraded to smart motorway, dual four all-lane running. The hard shoulder will be retained between junctions 7 and 8.

The scheme will involve:

  • permanent conversion of the hard shoulder to create a fourth lane and changing the junction slip roads to accommodate this
  • new CCTV cameras and electronic information signs and signals on gantries - these will show variable mandatory speed limits and manage traffic flow and incidents
  • emergency refuge areas throughout the length of the scheme
  • the hardening of the central reserve and installation of a reinforced barrier to improve safety

In order to implement the recommendations of the government review, the scheme will include stopped vehicle detection technology. It is expected to be complete in spring 2022.

See the overview of the M27 smart motorway scheme on the Highways England website and you can keep up to date with the smart motorway works by subscribing to the Highways England newsletter.


For more information on smart motorways, including a network map, go to Smart motorways evidence stocktake - Highways England.