M23 junctions 8 to 10: smart motorway

Upgrading the 11 mile (18km) stretch of the M23 near Gatwick Airport, between junction 8 near Merstham and junction 10 at Copthorne, to an all-lane running smart motorway.

Start date 2017-18
End date 2019-20
Cost £164 million

Latest updates

  • 01 April 2020

    Installing smart motorway technology

    Work will continue overnight to install technology so this stretch of the M23 becomes a fully operational smart motorway. Stopped vehicle detection technology will be added in the future, as set out in the Transport Secretary’s smart motorway action plan.

  • 31 March 2020

    Work completed on an additional lane

    We've completed work on an additional lane to increase road space. A 50mph speed limit will remain in place as well as CCTV monitoring and a free recovery service.

Project information


The M23 is a crucial part of the UK strategic road network connecting Crawley and Gatwick Airport to the M25 motorway, routes into London and the rest of the UK. This stretch of the M23 is heavily used by traffic travelling to and from Gatwick Airport and between Brighton and London, especially during UK holiday periods.

As a result safety, congestion and journey times are all key issues that need to be improved. As junction 9 of the M23 is the main access for traffic travelling to and from Gatwick Airport, this scheme is of particular local and national economic and political importance. 

The junction 10 London-facing slip roads opened in December 2019, making the new junction 10a fully operational. A new junction and link road scheme are being constructed to help reduce congestion and accommodate the planned developments in the area. 

This scheme aims to: 

  • reduce congestion by smoothing the flow of traffic to improve journey times and make them more reliable 
  • facilitate economic growth within the region, by providing much-needed capacity on the motorway 
  • maximise motorway capacity while maintaining safety 

The scheme will enable proactive management of the M23 carriageway, including the link roads from/to the M25 at junction 8, the spur to Gatwick Airport and to junction 10. 

The scheme includes: 

  • converting the hard shoulder to create a permanent fourth lane between junctions 8 and 10 
  • converting the westbound hard shoulder along the spur to Gatwick Airport (towards Junction 9a) to create three permanent lanes 
  • redefined junction layouts to accommodate the fourth lane - in particular we're creating a dedicated northbound slip road before junction 9 to minimise congestion as traffic leaves the motorway and heads towards Gatwick airport 
  • new gantries with variable message signs, providing customers with better information 
  • installing new electronic information signs, signals and CCTV cameras - these will be used to vary speed limits and manage traffic flow and incidents 
  • installing 12 emergency areas to use in place of the hard shoulder which include emergency roadside telephones and CCTV cameras to improve emergency service response times 
  • improving the central reserve and adding a reinforced barrier to improve safety 
  • adding new noise barriers in built up areas 
  • carriageway widening to provide new acceleration and deceleration lanes to our maintenance facility, Weatherhill Depot 
  • creating a new emergency turn-around facility at Coopers Hill Road to minimise our response times to incidents 

2017-18 Consultation - 11 December 2017 - 15 January 2018 


Traffic information

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

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