Without fuss last week, the City of London's 'restraint cordon' was expanded by 40%. After a 12 month trial, St Paul's, the Barbican and Bart's Hospital are in, giving them extra security and pedestrian safety and gaining goodwill from local businesses and residents. More significantly, Islington, Hackney and Tower Hamlets are sold on the merits of the cordon and will soon add a further northern chunk to the enclave.
Most of the public know the cordon as the 'ring of steel', although engineers call it the 'ring of plastic' because of the red and white cones and barriers marking the boundary. I suspect that all of us believe it was the direct result of the IRA's attack on the City of London in April 1993. The truth is that the traffic management revolution was due in May 1993 anyway and had gained all the necessary approvals beforehand.
Joe Weiss in the City engineer's department was charged with the big change, and he summarises what happened by referring to two Evening Standard billboards: on Monday morning 'Fortress City: traffic chaos alert', by afternoon 'City's Ring of Steel success'.
Although the City has special characteristics, Weiss believes its example could be applicable in other towns and cities. Whether Deputy Prime Minister and DETR supremo John Prescott shares his conviction will become obvious when the government publishes its White Paper shortly on integrated transport policy and spells out the steps it plans to take regarding traffic restraint.
Since 1945 the Square Mile's planners have allowed only one parking space for every 12,000 sq/ft of new offices built, and on-street parking now costs £3 per hour. Traffic from Monday to Friday has stayed constant for the last 10 years at 250,000 vehicles a day, 70% of it through traffic. The City fathers still insist that businessmen should be able to drive in to sign deals or enjoy lunch, but they have accepted that within the cordon, priority should switch to pedestrians whose movements - quaint terminology that - exceed 600,000 trips a day, more than double that of vehicles.
The ambition was to achieve a win-win for just about everyone involved. By changing traffic signals and closing side streets, through traffic does move around the cordon quicker. While not prevented from entering the core, drivers who choose to do so find progress slower due to entry points manned by police and lights favouring those on foot.
The full scheme was introduced over one weekend in July 1993, two months after the IRA bomb. Streets closed numbered 17, 13 others reverted to one-way working and traffic signal timings were changed at 23 junctions. All had been modelled on nothing more complex than Saturn.
Daily traffic entering the City still stands at 250,000 but 40,000 trips no longer enter the core, a 25% reduction equivalent to a queue of cars from Harrods to Cardiff. Bus journey times have not changed, but the route along the Embankment carries 20% more traffic with shorter journey times.
Air pollution has reduced by 15%, more than enough to make up for the growing numbers of young women and men who smoke cigarettes on the steps outside their offices today.
Weiss does not pretend that there are no losers, but the winners are far more numerous. In three years, fewer than 30 written complaints have been received. Two major banks just outside the new cordon have campaigned to be brought inside, and an NCE colleague is currently lobbying Hackney to get his street included in the next extension.
This type of traffic restraint is appealing in its simplicity, and if it means that more police are needed on the streets that is a modest price to pay. Only the four digital cameras checking each entry queue can be said to be high-tech, and it is claimed that these can detect stolen vehicles before they reach the cordon.
I get worried when I hear of hundreds of traffic engineers dreaming up ever more complex ways of charging motorists either for driving or for parking in private as well as public places.
In my experience they are too often bamboozled by their own pseudo technology. Keep it simple and give the City solution a try first.