Transportation reform advocates say roads and parking lots are fertility drugs for cars. This seems obvious to anyone who looks at our cities and suburbs, and has even been borne out by some academic and government studies. The corollary of "build and they will come" is "remove, and they'll stop coming." A new British study examines this principle and finds the data support it.

The study team was led by Professor Phil Goodwin of University College in London and included analysts for London Transport and the new Dept. of Environment, Transport and Regions (how come the FHWA and the MTA never do anything this interesting?). They examined 60 cases worldwide where roads have been closed or had carrying capacity significantly reduced. Their findings show that, on average, 20% of the traffic that had used the road seems to vanish and that the number was as high as 60% in some cases. Significantly, the finding was true in urban and non-urban places alike.

One of the best documented cases in the report involved London's Hammersmith Bridge. It was closed to all traffic except buses and bicycles in 1997. Before and after surveys found that of those who drove at the start of 1997, 21% no longer did after the bridge closed.

Although it's unclear whether the study looked at principally British examples, the shrinkage principle has been demonstrated periodically in NYC. Traffic chaos predicted when Fifth Avenue was severed at Washington Square Park in the 1950's never materialized. On a larger scale, the sudden collapse of the West Side Highway in the early 1970's failed to produce more than a ripple on other area arterials.

The work is described in New Scientist magazine. The Campaign will obtain the study itself in the near future.