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: