Worst case scenarios suggest up to 20,000 cars could head for Bristol when Cabot Circus opens tomorrow.

As well as from the city itself, people will be drawn to the new shopping centre from far and wide, along major arterial roads and public transport networks.

You can almost picture it from above – columns of traffic marching incessantly towards the middle of Bristol.

So will the city, already struggling to contain the thousands of vehicles which stream in every day, cope?

A recent survey has shown that Bristol West and Bristol East already both sit firmly inside the top 10 most congested constituencies in the country.

And the Highways Agency has issued a warning suggesting motorists – including shoppers and commuters – avoid the M32 for the “first few weeks” after the new stores open.

The pessimists may fear traffic chaos but those in charge remain cautiously confident that the measures put in place will manage the traffic.

The city council has done a lot of work in advance of Cabot Circus opening.

Measures like Newfoundland Circus and the redesigns of roundabouts like Junction 3 of the M32 and the one at the bottom of Jacob’s Wells Road in Hotwells are obvious changes.

But the fine-tuning of traffic light sequences, for example, is a less obvious alteration which is expected to make a big difference. The sequences will be supervised by the city council’s new urban traffic control centre, which opened last week.

Other measures include expanded car park capacity at the park and ride site on the Portway, with the Highways Agency using signs to encourage those  on the M4 to drive around to use the facility. Opening hours will be extended at  park and  rides in Brislington, Long Ashton and Avonmouth – until 8.35pm from Monday to Friday and until 8.25pm on Saturday.

The University of the West of England  car park at Frenchay, which is used as a park and ride site in the build-up to Christmas, will be available at weekends, starting this Saturday.

But there is no disguising the fact that the city is crying out for somewhere for cars be parked  near  the junction of the M32       and M4 and use the new bus lane on which the city council is spending £3 million.

 Richard Belt, the centre director of Cabot Circus for developers the Bristol Alliance, said: “It would be great to have a park and ride at the top of the M32, absolutely, but it looks like it won’t happen until 2011.

“But peak time will be the weekend and we have the UWE car park to use then so, while we would urge the authorities to sort the permanent site out, we have done what we can.

“I’m as confident as I can be because we have been working with Bristol City Council for the last 10 years leading up to the development.

“A lot of the work involves changes to the motorways and the park and ride at the Portway but we have also been speaking to all the various transport groups to make sure that we have done the best we can.

“What we would really ask is that people plan their journeys and avoid using the car whenever possible – there are lots of other options.”

Extra car parking spaces have been provided in the scheme, with the 2,600 capacity multi-storey construction on the edge of the development.

Drivers will pay £3 to park for up to two hours in the new Cabot Circus car park. Between two and four hours will cost £5, four to six hours will cost £8 and up to eight hours will cost £12, from Monday to Saturday.

Up to 24 hours costs £16 with all-night parking, from 6pm to 7am, will cost £2.50 and people will also be able to park for £2.50 for up to four hours on Sundays.

The volume of vehicles which Portway park and ride can handle  has been doubled to 520 and will  use a newly-extended bus lane into the city.

Signs around the city will be updated every five minutes to say how many car parking spaces are available.

Mark Bradshaw, the city councillor in charge of transport, said: “Managing traffic is a major daily priority for the council. We monitor our performance constantly.

“Ahead of Cabot Circus we have invested serious amounts of money in the best technology and physical road improvements to reduce levels of congestion.

“However much we invest and whatever we say about the range of travel choices available, much will continue to depend on how people choose to travel.

“The city council has invested in local rail, the ferry service, improved walking and cycling access and worked with the transport operators and the Bristol Alliance to provide the widest range of travel choices and better more accessible information.

“People can see examples of this commitment to  our city in,  for example, the new traffic signs, the M32 bus lane, the ferry shelter in Castle Park, and the expanded Portway park and ride, and extended bus lane.”