During the closure, southbound M3 traffic will be diverted off the M27 at junction 14 to follow a diversion via the A33, A27 and A335. M27 traffic will be diverted onto the northbound M3 to j12 to follow a diversion via the A335 to rejoin the M27 at j 5.
Traffic approaching from London or the north will be encouraged to use the A3 rather than the M3. The safety improvement work involves reprofiling the surface of the carriageway between junctions 4 and 5 - angling the carriageway to allow surface water to run off the surface more efficiently.
The work and diversion routes have been carefully planned in liaison with the local council and police, so it can be completed safely while keeping disruption to a minimum.
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One person has died following a crash on the A31 overnight. The road is still closed with long westbound diversions through the New Forest.