Sonoma County's latest go-around with Eurocentric driving habits has opened to mixed reviews near Glen Ellen.

"I hate it," said a woman who gave her first name as Virginia and lives near a new roundabout at Arnold Drive and Agua Caliente Road.

Jeri Willis, however, said her husband went through the roundabout and liked it.

"He said it goes smoothly," Willis said at her Don Timoteo Court home Friday.

The roundabout's debut on the well-trafficked county road has long been anticipated, and in some quarters, dreaded.

Supporters say the roundabout will ease congestion at the intersection, reduce the risk of crashes and prove better for the environment because vehicles won't be idling. Critics, however, view it as a waste of taxpayer money and possibly a greater threat to motorist safety than had the county installed a stop light at the intersection.

The roundabout is at the entrance to the Hanna Boys Center and features a one-lane traffic circle in which vehicles move counterclockwise around a center circular island, entering and exiting to the right. The motorist entering the roundabout must yield to traffic already circling.

Most motorists appeared to grasp the concept, despite the added visual distraction of crews working with heavy equipment in the roundabout's center.

The driver of a flatbed truck ferrying a half-dozen vehicles navigated the circle with no problem, as did the drivers of other large vehicles. A passenger in a pickup that went through the circle waved his arms around and around in an apparent attempt to explain the concept to the driver, who had a puzzled look on his face.

Controversy has trailed the project, which is budgeted for $2.08 million. The Sonoma Valley Citizens Advisory Commission in 2011 narrowly endorsed the project in a split 5-4 vote. Neighbors also aired dissenting views at a meeting held to gather public input.

The roundabout is partially funded by Measure M, a quarter-cent sales tax approved by voters in 2004. The tax money also is being used to study the possible implementation of a roundabout at the three-way intersection of Highways 116 and 121/12 in Carneros.

Nowhere in the original ballot measure does the word "roundabout" appear. Rather, voters were told improvements planned at Arnold Drive and at the Carneros intersections would include installation of "traffic signals."

Traffic planners acknowledged that fact in May when county supervisors awarded a $1.90 million construction contract for the Arnold Drive roundabout to Team Ghilotti Inc. In addition to the traffic feature's other touted merits, planners said the roundabout resulted in the removal of fewer trees and no impact to three creek crossings that would have been disturbed with the signal option. It also required less right of way.

But another Don Timoteo Court resident who gave his name as J.B. called the roundabout a "waste of money."

"I've never had a problem. I don't see why they need to put it there," he said.

Virginia, who lives on Agua Caliente Road, predicted the roundabout will confuse motorists and do nothing to slow traffic on Arnold Drive.

"I understand roundabouts. A lot of people don't," she said.

Cotati voters enacted a permanent ban on roundabouts in 2012, likely making the city the first in the nation, and possibly the world, to take that step. A roundabout planned for Highway 116 at Mirabel Road in Forestville also has been met with resistance.

In Healdsburg, a roundabout planned at the intersection of Healdsburg Avenue with Mill and Vine streets has generally garnered more enthusiasm.

You can reach Staff Writer Derek Moore at 521-5336 or derek.moore@pressdemocrat.com. On Twitter @deadlinederek.