New traffic circles are being installed at two Ballard intersections that ranked as high priority for "calming measures" based on collision, speed and traffic volume statistics.

Traffic circles are being put in place at Northwest 64th Street and 22nd Avenue Northwest and at 10th Avenue Northwest and Northwest 67th Street. It's part of the Seattle Department of Transportation's 2008 Traffic Circle Construction Program.

Each circle costs approximately $15,000 to design, install and construct said Marybeth Turner, a spokesperson for the transportation department.

Intersection crashes account for approximately 45 percent of all collisions in the country, according to a 2006 Federal Highway Administration study. Traffic circles have been proven to prevent and even reduce intersection crashes.

Though traffic circles may have different operating rules in varying cities, on Seattle non-arterial streets they are typically a center island in which traffic flows around in one direction. Traffic enters and exits through right turns only, making the chance of impact less likely.

Each one must be designed to meet the needs of drivers, emergency vehicles, pedestrians, bicyclists and people with disabilities.

Every traffic circle in the city has been built because of a request from a citizen who lives near the intersection. Seattle has more than 1,000 traffic circles and receives about 150 requests for them per year, said Luke Korpi, who oversees the traffic circle program for the city.

After a request is made, the city evaluates the safety record of the site based on how many crashes have occurred there. If it's found to warrant a circle, the applicant must gather signatures from at least 60 percent of the households and or business owners within one block of the proposed site. If enough people support the project, the department of transportation then conducts speed and volume studies for that intersection.

After construction, the circle is monitored for up to one year, when traffic speeds and volumes are measured to analyze how effective the tool is.

Community members must agree to maintain landscaping in a traffic circle, otherwise it is covered with asphalt or concrete. The city supplies the soil and plants, but planting and long-term maintenance is up to the community, said Korpi.

Both new Ballard traffic circles will have landscaping.

The types of plants chosen depend will on height capability - to ensure visibility - and drought tolerance.

Rebekah Schilperoort may be reached at 783-1244 or rebekahs@robinsonnews.com.