They've been popping up all over town, providing relief from traffic congestion, but confusing some drivers.
And now that Petaluma's eighth one has been installed, issues related to traffic safety and driving rules have been surfacing.
They're roundabouts, a British word dating back to the early 20th century that refers to road junctions where traffic moves in one direction around a central island.
Often, roundabouts are installed in areas where traffic frequently is congested. They facilitate passage through these areas by eliminating stop signs and signal lights.
"When looking at areas with high collision rates, a viable solution is a roundabout," said Sgt. Ken Savano of the Petaluma Police Department. "We support roundabouts, because they reduce the number of conflicts that drivers have in getting through an area quickly.
"They reduce drivers' speeds and keep people moving."
He says that after roundabouts were installed, only a handful of accidents have occurred at the intersections, which generally had been problem spots.
Savano feels that most local residents are familiar with roundabouts and understand how they operate, although recently licensed drivers can get puzzled.
"And I've seen some people who are new to the city get confused, because they're not familiar with them," he said.
; The California Vehicle Code offers these guidelines:
; Slow down as you approach the roundabout.
; Yield to pedestrians and bicyclists crossing the roadway.
; Watch for signs and/or pavement markings that guide you or prohibit certain movements.
; Enter the roundabout when there is a big enough gap in traffic.
; Drive in a counter-clockwise direction. Do not stop or pass other vehicles.
; Use your turn signals when you change lanes or exit the roundabout.
; If you miss your exit, continue around until you return to your exit.
The Vehicle Code states that for roundabouts with multiple lanes, choose drivers should choose an entry or exit lane based on their destination. For example:
; To turn right at an intersection, choose the right-hand lane and exit in the right-hand lane.
; To go straight through an intersection, choose either lane, and exit in the lane you entered.
; To turn left, choose the left lane, and exit.
Savano emphasized that although drivers encounter yield signs when approaching roundabouts, they are allowed to enter even if other drivers are inside them.
"They can get in roundabouts either in front or in back of the other vehicles, as long as they don't interfere with them," he said.
Once inside roundabouts, vehicles should not stop to allow other vehicles to enter, he said.
While Petaluma's roundabouts have the same basic design, they vary in some ways.
"They are designed to fit the existing conditions," said Curt Bates, the city's traffic engineer. "Each area where they have been installed has a different topography, and we design each roundabout to accommodate the existing features."