It is not as illogical as it sounds. Already this idea has been accepted by the Department of Transport in relation to motorways. The busiest part of the M25 has been fitted with devices that can vary the speed limit so that when the road is particularly busy it is reduced from 70mph to 60 or 55. And hey presto, more cars are able to use it, as the stop-start effect of people speeding up and then being forced to brake is dissipated. Other motorways are being similarly fitted with these signs.
The PSI pair, Stephen Plowden and Mayer Hillman, go further by suggesting that the effect could also work in urban areas. Researchers in Vaxjo, Sweden, found that the traffic flowed more smoothly at junctions when the speed limit was reduced because there was less stopping and starting.
Moreover, any time lost by some motorists would be partially made up by pedestrians gaining time as crossing roads became easier and involved fewer detours - in general, one person's lost time is another person's gain. For years, that equation has been weighted in favour of the motorist rather than the pedestrian. Indeed, in the cost-benefit calculations used to assess the value of road schemes, the time saved by motorists is assigned a value of around pounds 7 per hour. But pedestrians' extra time is not counted as a disbenefit. That is why we have those ridiculous bridges over some dual carriageways where pedestrians are supposed to spend five minutes walking up spiral staircases to a height of 30 feet or more, simply to cross a road.
During the long rise and rise of the motor car, society lost its sense of proportion. Rather than being a means to an end - easier travel - cars became the centrepiece of transport policy. The space in towns was turned around to accommodate the motor car rather than the people in them. One- way systems were created to speed it along its way, while other road users, such as pedestrians and cyclists, were designed out of large swathes of urban areas. Barriers were erected to hem pedestrians in; traffic lights were installed to allow them to cross the road only for a few seconds every couple of minutes and high streets were turned into urban clearways as traffic was given priority at every opportunity. Speed became an end in itself. Little thought was given to the downsides, not only the casualties, but the degradation of the environment caused by fast cars.
The PSI book argues that it is time to reconsider this set of priorities. Instead of allowing cars to whizz about unfettered around towns, the authors suggest a speed limit of 20mph or 15mph. Outside towns, the authors want to see a 55mph speed limit as the most optimal between reducing the casualty rate and ensuring that road transport is still economic. The limits would all be enforced by speed limiters, similar to those fitted to lorries and coaches, which could be set to different speeds in towns or outside.
The benefits from much-reduced speed limits in residential areas are enormous. People, particularly the old and the young, would be freed to reclaim the streets. No longer would anxious parents have to accompany their children to school, old ladies would be able to walk to the shops again and children would be able to play in the streets safely. As a result of the streets becoming more used by people, crime would fall and communities would be revived.
Outside towns, the benefits are mostly in the form of reduced road casualties, but there would be environmental gains, too, through reduced fuel consumption.
Plowden and Hillman deny that they are being idealistic or outlandish. They are not suggesting that some people will not still resort to their cars even for ridiculously short trips to the shops. They accept that cars will remain an integral part of society's desire for mobility. But just by changing the hierarchy between cars and pedestrians, which has evolved without thought or debate, urban society will be transformed.
In answer to suggestions that all these ideas are merely the musings of radical transport planners, Mr Plowden replies: "Things are changing. Only a few years ago, walking and cycling were at the bottom of transport priorities. Now it is accepted that they should be at the centre of any transport policy." He adds that public opinion was ahead of the views of politicians in realising that the current use of cars was unsustainable. Many people involved in transport policy-making already support views similar to those of the authors.
Experience from towns such as York, where these ideas have been put into effect, suggest that after initial antipathy they become very popular. In York, the hierarchy of transport has been turned round, giving pride of place to pedestrians and cyclists, followed by public transport, and finally the individual car.
Indeed, visitors from abroad frequently comment on how traffic has been able to dominate the urban environment in most of our cities in a way that is now unthinkable in the cities of Holland or Germany. There is nothing to lose except our obsession with the car.
`Speed Control and Transport Policy', by Mayer Hillman and Stephen Plowden, is published by the Policy Studies Institute, pounds 14.95.