Drivers and travellers are being warned of overnight lane and sliproad closures around the M23 junction 9 roundabout near Gatwick starting from tonight (Monday).
The closures are to enable upgrading of traffic signals to improve traffic flows at times of congestion.
The Highways Agency say as much of it as possible of the work will be done at night between 8pm and 6am.
The work is necessary to upgrade the technology which monitors traffic flow including the systems which control the phasing of the signals which will be better able to detect congestion.
The work will be carried out using overnight lane and slip road closures and is due to be completed, weather permitting, on Friday February 7.
Robert MacKenzie, Highways Agency Project Sponsor said: “The traffic lights use sensors in the road to detect traffic flows and adjust the sequences to provide the best flow around the junction.
“The existing sensors on the bridge will be replaced with a new generation that are more reliable and require less maintenance to ensure that the traffic lights continue to keep the traffic moving efficiently.
“We have planned the work to be carried out overnight, when we know traffic flows are lowest, to minimise the disruption.
“During the final week we will be closing slip roads and I would advise anyone wishing to use the junction to plan their journeys and allow extra time.”
The work will carried out overnight, between 8pm and 6am, using lane closures and a 50mph speed limit on both carriageways.
The southbound exit and the northbound exit and entry slip roads will be closed for five nights from Monday 3 February. Fully signed diversions will be in place via junction 10, the A2100 and A23.
Signage will be displayed on the northbound M23 to advise drivers wishing to exit at junction 9 to use junction 10 to follow the diversion route.