Overnight lane and slip-road closures are due to be introduced at the M23's busy junction 9 roundabout near Gatwick from tonight.
The three-week-long closures have been announced by the Highways Agency (HA) to enable critical traffic signals to be upgraded to improve traffic flows around the key roundabout.
The improvements work is due to start tonight.
A HA spokesman said the improvements will involve upgrading the technology which monitors traffic flow. He said: “This means the systems which control the phasing of the signals 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, HA 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. “ He said: “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.”
He added: “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 is being 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, February 3.
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.
The Highways Agency is an executive agency of the Department for Transport which manages, maintains and improves England’s motorways and other strategic roads on behalf of the Secretary of State.