Similarly, a study in Portland, Oregon found that a pedestrian-friendly environment can reduce vehicle miles traveled by 10 percent. These substantial benefits, in addition, were achieved by increasing motorist trip time by an average of only 33 seconds. Receptive residents along the streets grew from 30 percent before to 75 percent after. Portland finds that traffic circles are most effective when constructed in a series. They are sometimes also located in the middle of the block.
Circles reduce motor vehicle speeds and result in a big reduction in the number of accidents.
Seattle likes circles so much that they build about 30 circles each year. Humps cause motorists to experience little or no discomfort at speeds up to 25 mph, and need to be spaced close enough to each other so that motorists do not speed between them. The ITE has found that despite concerns about liability, vehicle damage and emergency vehicle impacts, these problems have not occurred or have been found to be insignificant when considering the positive impacts of humps. And despite the conventional wisdom, stop signs do not affect overall traffic speeds or control speeding. Posting appropriate speed limits and enforcing them is not sufficient to achieve needed reductions in motorist speeds.