- In 1990, traffic accidents cost the nation up to $137 Billion in direct costs, lost time and productivity. Congestion costs were approximately $40
Billion in the 29 largest urban areas of the U.S.
- In Seattle, the City's traffic calming program has reduced pedestrian accidents by more than 75%. (Local Government Commission, 1997).
- A carefully designed roundabout can handle 30% more traffic than a signalized intersection, while reducing pedestrian accident rates by about 60%.
Emergence of the Modern Roundabout as a Reality in Vermont and its Relation to Vermont Urban Design and Development. Tony Redington,
1997.
- Constructing very nicely landscaped roundabouts cost about 10% less than a signalized intersection with no landscaping. Roundabout operation and
maintenance costs are minor. Signalized systems consume electrical power (up to $3,000 per year), require periodic roadway detector loops
replacement, and have major costs for upgrades and replacement.
- At peak hour, "stop delay" for three-legged roundabouts is about half that of signals; for four-legged roundabouts, "stop delay" is one third that of
signals. During non-peak hours, roundabouts routinely operate at Level of Service A (under 5 seconds delay).
- The aesthetic value of roundabouts should not be underestimated. Roundabouts can define a community gateway, enliven an intersection area, and
highlight adjacent historic buildings. The German word for traffic calming, verkehrsberuhigung, means more than making the traffic quiet, it
means making the surrounding areas better. R. Tolley, 1990.
- Accelerating from a stop is a major source of vehicle exhaust. Traffic calming can help reduce this pollution because stop signs are often removed
and replaced with traffic circles that allow cars and trucks to slow to about 15-20 mph while traveling through the intersection. Ozone precursor air
pollutants in San Francisco Bay Area Bay Area can be reduced by 2 tons per day if this technique and other traffic calming is widely implemented.
Air Quality Management District, 1997 Clean Air Plan, Transportation Control Measure # 20.
- About one-third of all accidents and injuries occur at intersections. On average, roundabouts experience about half the vehicle collision rate of other
types of intersection control. Damages are usually limited to minor vehicle repair - with none of the catastrophic damage associated with red light
runners. Relative Safety of Modern Roundabouts and Signalized Cross Intersections, Ourston and Doctors, Santa Barbara, California).
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