One of Cotati's biggest employers may have inadvertently undercut its objections to a city proposal to install two roundabouts on its main street.

<NO1><NO>Oliver's Market, which has said it won't relocate downtown if the traffic plan goes forward and may leave the city, has been showing a video to demonstrate how the roundabout would be an impediment to big trucks.

The traffic control circles are part of a $3.5 city plan to revitalize its small downtown. City officials favor it over another plan they came up with that would make Old Redwood Highway a four-lane road.

But Oliver's video, which company officials filmed, does not tell the full story of how Cotati's roundabouts would work.

The video, presented last week by Oliver's General Manager Tom Scott to the city's design review committee and promoted on the company's website, shows a semi-trailer truck negotiating a Petaluma roundabout that is said to be the same size as those in Cotati's proposal.

The truck circles the roundabout in residential west Petaluma several times, its rear two sets of wheels crossing into the roundabout's inner circle each time, leaving black tire-tread marks.

In a letter on the Oliver's website describing the company's opposition to the roundabouts, Scott directs readers to the video with a link.

But according to Petaluma officials, the roundabout in the video at West Haven Way and Windsor Road is 110 feet in diameter. The proposed roundabout on Old Redwood Highway in front of the site where Oliver's has planned its new store is 118 to 128 feet in diameter, according to Cotati officials.

There are other differences. The travel lanes around Petaluma's roundabout are 17 feet wide. In Cotati's version, the travel lanes are 22 feet wide.

The differences are significant when it comes to trucks,<NO1><NO> one expert said.

"It'll make a big difference going around," said Jose Campos, who runs JGC Truck Driving and Training in Santa Rosa.

"It would make it a lot easier with the bigger one," said the veteran truck driver. "It would be a tighter turn with the shorter one," he said.

It's common practice too, especially on larger trucks, to adjust the rear axle position to create a smaller turning circle when conditions require it, Campos said. In Oliver's video, the axles are set at the rearmost position.

Cotati Councilman Mark Landman found the video problematic. "That's a difficult thing for me and for everyone in the community," he said. "What we're looking for and need right now is good information on the project to help us make a good decision."

Scott downplayed the discrepancies, saying the video was made chiefly "to spur conversation."

"What is true is that a roundabout that size will handle a big semi. We thought it would be edifying to have the decision makers see what that actually is going to look like."

The company has not changed its position that if the roundabouts go in, it will call off its plans to build a new store downtown<NO1><NO>.

"They're meeting with us and we're hoping we can find a positive solution to this," Scott said. "We're not trying to kill something. We're trying to work with the city to build something."