IT should be the gateway to Southampton but has instead become one of the most notorious bottlenecks in the county.

The M271 regularly resembles a car park during rush hour as cars clog up the main route into the city whilst the stretch of road has become an accident blackspot due to the sheer weight of traffic.

Now highways bosses have devised a £25m plan that they hope will ease congestion and allow traffic to flow more freely into Southampton.

Engineers have drawn up proposals to upgrade the Redbridge roundabout in Southampton and ease the gridlock that occurs on the M271 motorway at peak periods - but the work will mean nine months of disruption whist the work is carried out.

A new left-turn slip lane will enable motorway traffic heading for the city centre to reach the A33 into the city without stopping at the roundabout.

The congestion-busting scheme aims to prevent huge tailbacks building up on the southbound side of the M271 as drivers queue on the approach to the junction.

Details are still being finalised but work is due to start in 2019 or 2010 and will take about nine months.

Highways England wants to stop container lorries clogging up the roundabout by providing them with a more direct route to the docks and in doing so cut emissions that have led to Southampton being branded a toxic city die to poor air quality.

A spokesman said: "The Port of Southampton is the second busiest in the country and is very important to Southampton and the UK economy.

"Substantial levels of freight and cruise passengers travel in and out every day on the motorway network.

"Maintaining a well-functioning transport network is vital to the competitiveness of the port and the continued development and success of Southampton."

The scheme involves a new "free flow" slip lane leading from the M271 to the A33 using existing highway land.

A public consultation due to start next month will include details of traffic management measures that aim to "minimise" disruption during construction work.

The Highways England spokesman said; "The proposals are still at the options stage. We'll begin putting together our construction and traffic management plans after our final proposal is announced in 2017."

Southampton City Council says the current road system means lorries heading for the docks get "tangled up" with other local traffic.

The council leader, Cllr Simon Letts, told the Daily Echo: "The idea is to get trucks moving more swiftly from the motorway to the dual carriageway.

"The roundabout is currently one of the key pinch-points in the local road network. It slows traffic going in and out of the city and anything that helps resolve that got to be positive."

Campaigners are hoping that improved traffic flows will also lead to a dramatic improvement in air quality in the Redbridge area.

The scheme coincides with the Daily Echo's Breath Easy campaign, launched earlier this month after it was revealed that pollution levels in the city are too high.

Poor air quality is responsible for 110 deaths in Southampton each year and is estimated to cost the local NHS £50 million annually.

Redbridge councillor Andrew Pope said he hoped that improved traffic flow would cut the amount of pollution caused by fumes belching out of stationary vehicles.

Eugene McManus, chairman of Redbridge Residents' Association, described air quality in the area as "awful" and said action was long overdue.

He added: "The M271 is the main arterial route into the city. Tailbacks are a daily occurrence and often result in motorists using other roads in the Redbridge area as a rat-run.

"The proposed new slip lane could make a difference."

Earlier this year placard-waving residents staged a protest against ever-increasing traffic levels in the area and the impact on air quality.

They spoke out again last month after major roadworks being carried out at junction one of the M271 at Nursling resulted in lorries being diverted down Gover Road. HGVs were subsequently banned from the route after householders voiced their anger.

Last night the proposed improvements to the Redbridge roundabout were welcomed by Associated British Ports (ABP), owner of Southampton docks.

ABP director Alastair Welch said: “Southampton is Britain’s biggest export port, handling £40 billion worth of exports each year and supporting 15,000 UK jobs.

"Any measure that helps it run smoothly is a win not only for the city but for the UK economy as well.”

Daily Echo:

The £2.3m scheme at junction three, designed to improve life for the 96,000 motorists that use the junction every day, started in October 2014.

Workers have been creating a third lane on the slip road off the westbound carriageway of the M27 and at both the northbound and southbound approaches to the motorway from the M271, along with additional traffic lights on the roundabout.