Major work is being carried out to transform Almondsbury interchange over the next two years.

The work, costing millions of pounds, will begin in March to improve traffic flow along the M4 and M5.

The hard shoulder will be opened up at busy times and overhead gantries will tell drivers of lanes to be used, speed limits and conditions, or crashes ahead.

Sensors in the road will count the cars and feed back to the Highways Agency control centre in Avonmouth.

With the help of cameras, the most-used interchange in the South West will be managed 24 hours a day.

Detailed plans and an informational film of the scheme were shown yesterday, and will be on show today at Cribbs Business Centre.

The project will cost the Department of Transport between £93 million and £140m and is expected to be up and running by summer 2012.

Tony Turton, senior construction manager for the Highways Agency, said: "This is one of the busiest motorway junctions in the country. The aim of this project is to make the roads safer, journeys more reliable and ensure drivers are more informed about traffic and congestion."

The scheme was announced by the Government earlier this year, following the successful managed motorway pilot on an 11-mile stretch of the M42, near Birmingham. There, accidents have been reduced, fuel consumption by vehicles has been reduced by four per cent and car emissions are down 10 per cent.

The area affected at Almondsbury will cover 2.5 miles of the M4 between J19 and J20; and 3.5 miles of the M5 between J15 and J17.

An average of 110,000 vehicles use the junction every day. The project will require 60 miles of cabling, 50 gantries and electronic signs to be built for advice and instruction to drivers.

When the hard shoulder is in use, emergency refuge pull-in areas 800m to 1km apart will allow broken-down drivers to pull in and phone for help. A red cross on signs over the hard shoulder will tell drivers when the lane is closed, while a speed limit warning indicates when the lane is in use. The speed limit for all lanes is reduced to 60mph when the hard shoulder is in use. An accident ahead will be indicated by a cross overhead.

Assistant project manager Jon Claridge said the scheme will create a lot of jobs for the region. "It will not just be the construction of the site that will create jobs," he said. "You will also have subcontractors, the technological industries – electronics, IT – the steel industries manufacturing the gantries. There is a whole supply chain that will be generated."

There are 27 planned managed motorway schemes in the UK but this is the only one for the region.

Howard Allbrook lives in Redland and has to used the interchange every day for his job in infrastructure. He said: "I drive along there regularly and it can be a nightmare during rush hour."

Ivor Humphries, 68, lives on the B4055 in Pilning and is not in favour. He said: "I think they are looking too much at the motorways. I think they need to look at the traffic lights at junction 17 of the M5, where it's grid-locked all the time."

The plans are on display at Cribbs Business Centre, Hollywood Tower Mansion, near M5 J17, from 8.30am until 3.30pm.