M27 underpass works: What you need to know

A section of the M27 is closed in both directions for 12 days as an "innovative" operation sees a new underpass slid into position.

We take a look at what exactly is planned and if there is anything drivers can do to avoid disruption.

Work has begun to move a huge concrete structure into position to form a new junction.

The 8,500-tonne, four-lane wide underpass is part of a £100m project run by Hampshire County Council and National Highways.

The M27 will be closed in both directions between Junction 9 for Whiteley and 11 for Fareham from 20:00 GMT on Christmas Eve until 04:00 on 4 January.

The council said the project involved "the creation of a new dual carriageway, with four roundabouts, to link the slip roads to the existing road network, forming a 'free flowing link' at Junction 10".

The new pre-built underpass will connect Fareham with the Welborne Garden Village development, which will eventually have 6,000 homes.

The council described the so-called "box slide" method utilised during the works as "innovative" and "pioneering".

It is the first time it has been carried out in Hampshire, and is "one of only a handful of box slide operations undertaken in the UK", it said.

Before sliding the new underpass into place, 24,000 cubic metres of material - about 10 Olympic sized swimming pools - needs to be excavated from the existing embankment.

After the structure, which is six double decker buses long, has been slid 65m (213ft) along the trench, the motorway will then be rebuilt above.

There will be a signed diversion route along the A27, mostly with two lanes in each direction, but it is expected to be busy.

Lulu Bowerman, Hampshire County Council's cabinet member for highways, has said the Christmas period was chosen because traffic levels are lower, but that road users should anticipate "severe delays" on the diversion route and around it, especially in the Fareham and Gosport areas.

She suggested travellers "maybe take public transport, travel earlier or later, try a different route, or even ask yourself if the trip is really necessary".

Drivers will be able to exit the M27 westbound at Junction 11 for Fareham and Gosport, and eastbound at Junction 9 for Whiteley and Park Gate.

There will be no westbound entry to the M27 at Junction 11 for traffic heading towards Southampton or the A32 (Alton), and no eastbound entry at Junction 9 for traffic heading towards Portsmouth.

The county council said advance inspections and repairs were carried out on the A27, and it was restricting any planned roadworks along the A-road during December and January.

Advance signage has been installed on the M25, M3, M4, A3, A27 and A34, including electronic messaging signs monitoring traffic in real time.

There will be traffic signal reprogramming at M27 Junctions 9 and 11, and the A27, to help manage traffic flows.

There is a free recovery scheme on the official diversion route, and a temporary traffic regulation order so that broken-down vehicles are "swiftly" removed.

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