Commissioned as British car ownership was climbing steeply, Traffic in Towns argued that traffic is a function of land use and therefore a planning problem rather than a highway problem. Its two devices were a hierarchy of distributor roads to carry movement, and environmental areas - residential, commercial or civic precincts - inside which environmental standards rather than traffic capacity set the rules. Worked studies of Newbury, Leeds and part of central London costed full motorisation, including multi-level traffic architecture that lifts pedestrians onto decks above vehicles. Buchanan drew on Alker Tripp's precinct idea of 1942 and on Perry's neighbourhood unit, and stated plainly that towns cannot absorb unlimited traffic without either being rebuilt or restraining the car.
It made circulation the organising logic of British urban planning for two decades, licensing ring roads, pedestrian decks and precinct clearance in dozens of town centres. Read the other way, the environmental area is the direct ancestor of traffic calming, the cell and superblock, and today's low-traffic neighbourhoods.
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