More than 600 traffic circles have been installed since 1978 as part of the city's traffic calming program, at a rate of 10 to 30 each year. After Seattle became known as one of the the most liveable cities and the economy flourished, the population of both humans and cars swelled. The main areas of complaint usually are within a block of an arterial road. A handful have been placed on collector arterials, as Seattle calls them, but those collector roads operate as residential streets. Another hidden but important issue, he says, is stop signs vs. traffic circles.
Nobody stops for stop signs.
In circles, you keep rolling. You may be going 15 mph, but at least you're moving. At stop signs, motorists try to make up for lost speed by gunning through the intersection. Nearby residents have to listen to grinding transmissions and screeching brakes. The City Council has funded circles, pedestrian walkways, circular bulbs, partial closures of streets and 'do not enter' signs.