Roadblocks ahead
- 24 January 1998 by Mick Hamer
- Magazine issue 2118. Subscribe and get 4 free issues.
- For similar stories, visit the Cars and Motoring Topic Guide
CLOSING roads cuts traffic, according to a report due out next month. The study, commissioned by London Transport and the Department of the Environment, Transport and the Regions, suggests that the computer models used by urban transport planners produce the wrong answers.
The report is also bound to lead to calls for the British government's White Paper on transport, due later this year, to include a radical programme of pedestrianisation and expanded public transport.
Computer models used by transport planners effectively assume that closing one road moves traffic elsewhere, causing congestion. But researchers led by Phil Goodwin of University College London, the government's adviser on transport policy, found that this is not what happens. The team analysed 60 cases worldwide where roads had been closed-or their ability to carry traffic significantly reduced.
Goodwin's draft report shows that on average 20 per cent of the traffic that used a road seems to evaporate after it has been closed. In some cases up to 60 per cent vanishes. The examples studied by Goodwin's team were mostly in urban areas. However, the same arguments may also apply away from major cities.
"There is more scope for traffic restraint," says Steve Atkins of London Transport, who was involved in commissioning the study. He described the results at the Institution of Highways and Transportation in London earlier this week.
The report is the logical extension of the finding that building new roads generates traffic, accepted in 1994 by the government's Standing Advisory Committee on Trunk Road Assessment. "If extra road capacity generates more traffic, then the closure of roads is bound to cause less traffic," says Keith Buchan, a London-based transport consultant who advises the government on traffic forecasts.
Many of the road closures studied by Goodwin's team were forced on the planners. In the summer of 1994, for instance, structural problems forced the City of London to close Tower Bridge temporarily. It is a good example of "traffic evaporation", says Joe Weiss, the City's assistant engineer. "Three years later the traffic had still not returned to its original level."
One of the best documented cases is London's Hammersmith Bridge, which has been closed to all traffic except buses and cyclists since February 1997 after routine tests found that the bridge was not strong enough to cope with its load of 30 000 vehicles a day. London Transport surveyed people using the bridge a few days before it closed, and were able to contact the same individuals in the following weeks. Of the commuters who drove to work across the bridge at the beginning of 1997, 21 per cent no longer drive to work
But where does the traffic go? The report reveals that the commuting habits of individuals can vary enormously, even when their journeys are not disrupted by road closures. On different days, the same person may drive, use public transport or work from home. This flexibility allows people to cope with road closures.
Experts suggest that the report could have an immediate impact on policy. "It's quite interesting for the proposed pedestrianisation of Parliament Square and Trafalgar Square," says Hugh Collis of the transport consultants Ove Arup. "They should just do it."
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[The report has been around for over a decade, but I get the feeling it would make traffic "planners" nervous here...]
The article is from http://www.newscientist.com/article/mg15721180.200-roadblocks-ahead.html
