A "CRAZY" diversion which will force HGVs and other large vehicles along one of Southampton's busiest high streets for around eight weeks begins on Monday.

Motorists have been warned to plan their commutes around the city as work to reconstruct Millbrook Roundabout starts.

The roundabout will be partially closed in four phases for 28 weeks until April next year.

The first phase of the roadworks will see the Redbridge Road slip-road to the roundabout, as well as the junction to Wimpson Lane and the exit from the roundabout onto Tebourba Way (northbound) closed.

To tackle the closures, city council bosses have created a five mile diversion for drivers along Shirley High Street from the West and Dock Gate 20 who are trying to get to the Waste Recycle Centre or First Avenue less than 200m away.

Motorists leaving Dock Gate 20 will be advised to go down Millbrook Road West before going around Redbridge Roundabout.

They will be then go back down Millbrook Road West and other the Redbridge flyover.

After this, they will turn down Regents Park Road, then Shirley Road and finally Tebourba Way before heading into the industrial estate.

Steven Galton, councillor for Millbrook, said: "I have some serious concerns over the proposed diversions - it seems crazy (given our congestion and air quality issues locally) to send HGVs to Shirley High Street and all the way to town to turnaround.

"I accept disruption is unavoidable, however could these works be completed faster and could there have been different mitigation plans put in place that avoided sending HGVs in to our most polluted part of the City twice as part of the diversion?"

The first phase works are expected to last until mid-November 2018.

It is part of an £8.3 million improvement scheme, which will involve laying a new road surface, installing updated traffic signals, and implementing a dedicated two-way cycle route.

A spokesperson for Southampton City Council said diversion routes for all roadworks in the city are determined by destination and suitable road category.

"We are confident the routes chosen for the Millbrook Roundabout works are the right options and in most cases they are the only options," said a startement. "We will be carefully monitoring driver behaviour through each phase of the scheme. If we find that there are specific network issues we will look at introducing additional traffic management measures where possible."

Following this work, the second phase will commence, ending December 19. This will see the closure of the roundabout junction with Tebourba Way (southbound) and the slip-road onto Millbrook Road West.

Phase three, from January 7 to March, will require the shutting off of the slip-road from Millbrook Road West on to the roundabout, as well as the exit from the roundabout onto First Avenue – which leads to Dock Gate 20.

Phase four, from March to late-April, will see the closure of First Avenue (northbound) up to the roundabout and part of the slip-road onto Redbridge Road up to the junction with Second Avenue.

The council spokesperson added that January to March is a “quieter time for the port” and “the only time when it would be possible” to close access into Dock Gate 20 for work to be completed.

However, the authority has confirmed that no works are planned to take place over Christmas. Millbrook flyover will also remain fully open throughout the works.