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Driving in Traffic Roundabouts

September 10, 1988

If drivers will plow through clearly defined signal lights at the peril of other drivers and themselves, what will they do at "Yield" signs where right of way is a matter of individual judgment? If they will generate gridlock by continuing into an intersection in spite of a red light and posted laws, can we expect them to politely wait their turn because of an unwritten "offside priority" rule which allows priority to circulating traffic?

Your roundabout article quoted Caltrans engineers as crediting the roundabout with a "40-60% decrease in accidents." Unfortunately, these statistics are about as meaningful as the ad which claims regular use of toothpaste results in "50% fewer cavities." Fewer than what? When the studies are examined more closely, they show that the only locations where roundabouts significantly lower accidents are where they replace previously uncontrolled intersections. A simple stop sign could also be expected to lower accidents.

A landmark study of modern roundabout safety by the British Transport and Road Research Laboratory (Green, 1977) compared before and after accident figures at 150 British intersections that had been converted to modern roundabouts. Of those, 60 showed an increase in either injury or fatal accidents, 26 showed no change. In fatal accidents alone, 32 intersections showed an increase, while 27 showed no change. At many of the intersections where a drop in accidents was reported, the measured decreases could not be statistically attributed to the roundabout itself.

In Ojai, a big issue was pedestrians, bicyclists, and mopeds, since the roundabout was to be built at a major intersection near three schools and a shopping center. British studies show roundabouts to be particularly dangerous for two-wheel vehicles, and no satisfactory way has been developed to allow pedestrians to safely cross several lanes of traffic that is continually moving in and out of a traffic circle.

Perhaps there is a place for the roundabout within the California traffic system, but the choice of a possible test site should require more scrutiny than Caltrans gave the proposed Ojai location.


Citizens for Safe Driving


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