Placer County might build roundabouts at these 3 intersections. Here’s where and why

Placer County is considering building roundabouts at three Granite Bay intersections near Folsom Lake and a high school.

A traffic subcommittee of the Granite Bay Municipal Advisory Council recommended roundabouts for two Douglas Boulevard intersections, at Auburn Folsom Boulevard and Barton Road; and one at Eureka and Wellington roads, next to Granite Bay High School.

The county Department of Public Works is seeking to answer three questions about the concept of roundabouts making their way to the area: are they feasible, does the community want them and, if so, how do they fund them?

Placer County and the advisory council contracted engineering consultant Kimley-Horn and Associates to conduct a study. They also hosted an open house to answer community questions and launched a survey to gauge support.

Gary Flanagan, who serves on the advisory council, first proposed roundabouts after roundabouts were built in Rocklin with a federal grant. He said they have seen success.

“I know when I see a good thing,” Flanagan said.

Engineers determined that the best choice for the three intersections based on cost and safety were roundabouts — multi-lane at the two larger intersections and a single lane roundabout at the high school — having evaluated the existing intersections compared to an improved traffic signal or a multi-lane roundabout.

Each of the three types of intersection was evaluated for cost effectiveness, including two societal costs — safety and traffic delays for drivers — and operations and maintenance. On all of these factors, roundabouts were significantly less expensive.

Initial capital costs were highest for roundabouts, which could cost up to $5.5 million, compared to new traffic signals which are estimated to cost $100,000.

The report also addressed possible constraints, such as existing gas stations at one intersection and cars with boats coming through frequently to get to nearby Folsom Lake, which designs would take into account.

Why consider roundabouts?

By reducing speeds and lowering conflict points, roundabouts have proven to minimize fatal and injury-causing collisions.

Not to be confused with the more common traffic circles, which have stop signs and signals, roundabouts only require drivers to yield as they enter the intersection.

Federal Highway Administration data shows roundabouts reducing fatal collisions by 90%, pedestrian collisions by 40%, injury collisions by 75% and overall accidents by 37%.

Collisions that do occur in roundabouts happen at much lower speeds. Cars usually slow to 15 to 20 miles per hour to go through a roundabout.

The selected intersections along Douglas Boulevard have seen some of the highest number of accidents in Placer County, as mapped by UC Berkeley’s Transportation Injury Mapping System.

At Douglas and Barton, 24 accidents have occurred right at the intersection and nearly another 30 surrounding the intersection between 2014 and 2022, the most recent data provided by TIMS. In 2023, an accident in the intersection killed a 15-year-old girl.

Auburn Folsom and Douglas has also seen more than 50 accidents at and around the intersection in the same time frame.

Cost analysis reported in the study showed that at Douglas and Barton, safety costs with roundabouts, which include injury, fatality and damages for predicted crashes, would be nearly a third of what they would be with a new traffic signal or optimized traffic signal.

Eureka and Wellington’s intersection has only one accident on the map, but sees a heavy volume of traffic, especially when high schoolers make their way to the nearby campus.

Roundabouts are becoming increasingly popular in the United States, though traditionally associated with European streets, and Granite Bay could be part of the growing trend.

Caltrans has recently been trying to get California, a state that has historically low numbers of roundabouts, on board with adding more. Sacramento has only a few.

Granite Bay’s neighbor Roseville has a few roundabouts that local drivers might have experience with, a multilane one at Washington Boulevard and Oak Street that has been there for a decade and a new roundabout at Washington and All America City boulevards, set to be completed later this year.

Roseville’s new roundabout is a required environmental mitigation measure for @the Grounds, Placer County’s fairground expansion, according to Helen Dyda, a city spokesperson. It also was intended to optimize traffic control in and out of the event center.

Studies have also shown proven environmental benefits of roundabouts because they increase the flow of traffic.

Unlike traditional intersections which require large volumes of cars to stop and wait, the constant movement of roundabouts minimizes idling and vehicle emissions, the Federal Highway Administration reported.

What do drivers think?

To gauge public reactions, Placer County hosted an open house Aug. 6 for interested residents to ask county officials and engineers questions and see data from the study.

Caltrans attributes California’s slow adoption of roundabouts to public perception and lack of familiarity with roundabouts. The state has nearly half the amount of roundabouts as Florida.

“When you answer all those questions…if somebody still hasn’t changed their mind, their bottom line answer is, ‘Well I just don’t like it,’” Flanagan said at the open house.

A QR code at the exit brought visitors to a survey that asked if they agree that roundabouts are safer and should be incorporated into Granite Bay intersections, and if so, which ones.

In the crowded open house room, many residents expressed doubts about the viability of multilane roundabouts on Douglas Boulevard and on residents’ ability to adapt to the change. There was more vocalized support for the smaller roundabout at Eureka Road and Wellington Way.

Survey results will help Placer County determine if they should ultimately pursue a roundabout project in Granite Bay and, if so, where.

“I don’t know what that decision is going to be, but if people listen, then they’re going to realize that there’s a huge safety factor,” Flanagan said.