Motorists facing M25 chaos

A giant section of the M25 is to be dug up - throwing thousands of commuters into chaos.

Holmesdale tunnel, which carries motorists along the congested orbital motorway past Enfield, will be partially closed for a major refurbishment from the autumn.

At the same time the sliproads at junction 25, adjacent to Holmesdale tunnel at the north of the motorway, will be closed to traffic.

The massive ?57million programme will stretch over one mile, take 100 engineers 18 months to complete, and cause disruption for 125,000 motorists who use this section each day.

The work will overlap with the existing ?147million project to widen the motorway to the west, near Heathrow.

The Highways Agency today revealed plans for the new scheme - and warned travellers to plan alternative routes or leave up to half an hour extra to complete their journeys.

When the work is completed, however, the M25 will be rid of a notorious bottleneck that has put a stranglehold on the motorway for more than a decade. In the first stage of the operationthe 650-metre tunnel will be boosted from three lanes in each direction to four, giving traffic more room to merge after it joins the motorway at junction 25.

To enable the work to go ahead each of the tunnel's huge twin bores will in turn be closed to traffic - allowing motorists to use a dual-carriageway contraflow in the remaining bore.

The speed limit will fall from 70mph to 40mph, further slowing up traffic.

Engineers will install powerful new ventilation fans in both sides of the tunnel to ensure that exhaust fumes are carried out safely.

Drains and lighting will be upgraded and a walkway created for motorists whose cars break down in the tunnel. A new CCTV system will also be installed for safety reasons.

Meanwhile, junction 25 will be upgraded from two lanes in each direction to three, enabling traffic to flow more freely.

New gantries will be installed to give motorists clearer directions - and the Agency will carry out extensive planting to mask fivemetre-high ventilation ducts to be built on top of the tunnel.

The Agency aims to complete the entire programme by spring 2007, and is mounting an exhibition on the project today and tomorrow at The Capel Manor Primary School in Bullsmoore Lane, Enfield.

The designer and contractors who will carry out the work are to be appointed soon.

" The work will lengthen journeys by up to half an hour during the works and local roads will be busier too," said a Highways Agency spokesman.

"But when the work is completed it will make the whole area run much more freely and improve journey times for commuters on the M25."

Work on the western section of the M25 near Heathrow should be completed later this year.