Just suppose that you could stroll from the National Gallery to Poet's Corner without crossing a road...

Imagine being able to amble freely, head in the clouds, from the early Italian Renaissance rooms of the National Gallery in London, across Trafalgar Square, down Whitehall and through Parliament Square all the way to Poets' Corner in Westminster Abbey.

No chance of being run over by raging motorists, no stepping around civil servants' cars parked shamelessly in Horse Guards Parade. Enhanced settings for famous buildings and all but forgotten monuments.

A Millennium project to transform the heart of Westminster - "World Squares for All" - was announced yesterday by Westminster City Council. Consultants led by the architect Sir Norman Foster have drawn up a plan to connect Trafalgar Square, Horse Guards Parade, Whitehall, Parliament Square and the Thames at Hungerford Bridge via a chain of pedestrian spaces and links.

The project, funded to date by the Heritage Lottery Fund (pounds 125,000), the private sector and the consultants (pounds 125,000), is to be the subject of public consultation in June and July. A revised plan will be implemented soon after so that "substantial elements", according to Westminster City Council, "will become a reality by ... 2000."

The consultants have produced options which include banishing traffic from nearly all of Trafalgar and Parliament Squares. Yesterday Sir Norman said at least a dozen major European cities had introduced pedestrianisation schemes on a similar scale. The costs of making the changes would range from a few million pounds to pounds 20m at the most.

A visitor to the National Gallery today walks out on to a narrow strip of pavement separated from Trafalgar Square by a tide of fuming traffic and crazed cyclists. It is, by the standards of the world's great squares, a barren space dominated for most of the year by pigeons and, on New Year's Day, Scotsmen splashing in the fountains while Nelson on his column turns a blind eye. With Foster and Partners on board, Londoners can rest assured Trafalgar Square, Horse Guards Parade and Parliament Square will not become "heritage"-style pedestrian precincts.

The "World Squares for All" project is not aimed at transforming the heart of London into a pedestrian play-pen or a heritage theme-park. The scheme aims to improve the flow of public transport and taxis, improve safety and minimise the diversion of "any consequential increases in traffic congestion and pollution."

This does raise the question, which Foster and his fellow consultants have yet to tackle in any detail. If traffic is to be throttled along these arterial roads, where will it go? Without a co-ordinated plan and without an enhanced London Transport in public hands, improvements to Trafalgar Square and environs well rob Peter to pay Paul.

Millennium plans for London need a degree of co-ordination that is impossible to achieve while life in the capital is increasingly subject to the uncertain laws of the market. Even so, the transformation of Trafalgar Square from a pigeon feeding area and an annual bath for Scotsmen into a great urban meeting-place can only be a step in the right direction.

World cities that square up to the new pedestrian age

Although many businessmen and council leaders have always claimed local economies suffer if cars and their wealthy passengers are excluded from parts of city centres, there is growing evidence that pedestrianisation can be financially beneficial. In cities across the world pedestrians are finally starting to win the battle with the car.

YORK: With its historic sites and traffic congestion, the centre of York was desperate for restrictions on the number of cars clogging its narrow streets. Pedestrian zones were introduced in1987, and since then vehicles have been excluded from around the cathedral. In an area of seven major streets vehicles are excluded from 11am to 4pm during weekdays and noon to 4pm on Sundays.York aims to be the first city in Britain to take control of traffic, rather than being controlled by it. By 1994, 20 per cent of all roads had been traffic calmed, and on unpedestrianised streets in the centre the speed limit is 20 mph. Accidents are down by two-thirds.

MILAN: Banning cars is relatively common in Italy, and to liberate the congested heart of Milan the authorities have pedestrianised streets and tried to improve the design of the area. To limit traffic chaos in the city centre, the authorities introduced a scheme where any vehicle entering the centre must have a permit. The permits, which have acquired the status of a winning lottery ticket, are given to all residents, a limited number of employers and delivery vehicles within certain hours. Despite initial opposition to the scheme - court cases and protests - the local economy seems to have benefited and shops are reporting increased turnover.

BOSTON: Planners say Boston is unusual among North American cities because the streets have evolved "organically", rather than along the typical grid and block structure. As well as improving bicycle routes and introducing traffic-calming measures in the centre of the city, the Boston authorities are "undergrounding" one of the major arterial roads and turning the area above ground into parks. Roger Graham, a transport and land-use planner, says that one of the most innovative schemes in North America is to be found in Portland, Oregon, where a "skinny-streets" initiative - limiting the width of streets, curbing the speed of drivers and the amount of traffic - is operating.

SYDNEY: Sydney is a relatively new city with wide, open streets where congestion is less of a problem than in London or other British cities. However, the authorities have pedestrianised Martin Place, one of the city's most important shopping streets, and have introduced traffic-calming measures, including the use of road humps and traffic islands. In Adelaide and Brisbane the authorities have also pedestrianised major streets with a resulting increase in turnover for the local economy.