roundabout couplet

Around we go again — The Healdsburg City Council selected a roundabout couplet alternative for the city public works department to consider for the Dry Creek Road and U.S. 101 intersections. The other option was signalized intersections, which was the less expensive option.

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City public works to explore funding options for possible roundabout project

The creation of a roundabout couplet at Dry Creek Road and the U.S. Highway 101 ramp intersections is becoming more of a possibility after the Healdsburg City Council voted unanimously on Oct. 5 to explore the roundabout option, giving the green light to city staff to research the option and to look into funding possibilities.

The council decision allows city public works staff to explore funding options for the estimated $5.7 million project, but it doesn’t set the roundabout in stone, and future councils could alter the decision if they so choose.

An estimate of the timeline for the project sets its possible completion two to four years out.

According to Healdsburg Public Works Director Larry Zimmer, a feasibility study and report was conducted in August of last year to determine viable alternatives at the interchange to help reduce traffic and improve traffic flow and pedestrian and bicycle access.

“This report was instigated by the need to accurately assess fees to current and future development. Concurrent with the Dry Creek feasibility study, staff has also begun preparing an Impact Fee Study with a consultant, Willdan Financial Services. Willdan is preparing a fee study for drainage, parks and Traffic Impact Fees. Staff has compared and analyzed both the proportional fee calculations done by the subconsultant and the city-wide impact fees calculated by Willdan,” the agenda item report reads. “The methodology and results from both are very similar. Staff will likely recommend using the updated Traffic Impact Fees, which will be coming to council for discussion at a future date. Since there is a difference in project cost between the two alternatives, and the preferred alternative using a roundabout couplet is the more costly alternative, staff is recommending council select an alternative by resolution so the future impact fees are calculated using the estimated cost for the alternative we intend to build.”

The study came up with two options, interconnected traffic signals at both intersections, or a couplet of roundabouts with a roundabout at each intersection.

Zimmer said a “no build” option was not feasible due to the volume of traffic that travels through the two intersections and the increased traffic that is anticipated following the completion of several developments such as the Montage Resort and the Mill District.

“There is just too much traffic going through that intersection,” Zimmer said.

“Alternative one is a standard signalized intersection. Pedestrians would be required to cross at Grove Street and that is going to be the same for both alternatives. Additionally, the northbound off ramp would have a dedicated lane and there would be an additional lane on Dry Creek,” Zimmer said. “Alternative two is the roundabout couplet … and they would fit in the same existing right of way. The cost estimate is very comparable to the signalized intersection.”

The rough cost estimate for the traffic signals is $5.25 million and the estimate for the two roundabouts is $5.7 million.

The estimates only include construction costs and if you escalate the approximate cost for the construction year, which could be a few years out, the roundabout cost would be around $7.15 million, plus design, environmental work and construction management.

Funding possibilities include revenue from development impact fees and county, CalTrans, state and federal grants.

In terms of the pros and cons for each option, the signal option would create a smaller construction footprint and wouldn’t take as long to construct as the roundabouts, however, it would create greater long-term maintenance costs and more points of conflict for drivers and pedestrians.

A roundabout couplet has lower long-term maintenance costs and would have less fixed objects on the roadway, making it safer in terms of possible pedestrian or vehicle collisions. The roundabout option would also lead to less vehicle idling and thus fewer emissions and fuel consumption.

On the other hand, the construction of the roundabout would create a much larger construction footprint and would disrupt the regular flow of traffic and it would take longer to construct.

The stages of a project such as this include crafting the concept and conducting a feasibility report — which has already been completed — creating a project initiation document (PID), creating a project approval document and getting approval from CalTrans and the county, creating a final design and review process, and finally, awarding a contract for construction.

Creation of a PID alone could take up to a year, and project approval and the final design could take up to two years, before construction is started.

Councilmembers voiced support towards pursuing the roundabout option and Councilmember Joe Naujokas said despite the time it takes to construct a roundabout, he believes it is a superior option.

“Even though the complication of the construction of the roundabout can certainly be a factor, I think the way that traffic flows and how the energy of the vehicle flow is moderated to me is such a far superior experience, both as a driver and a pedestrian. It is a technology that is proven that more and more communities are adopting,” Naujokas said.

Resident Mark McMullen also offered support towards the roundabout and said it would be nice to see some sort of art aspect incorporated into the roundabout design as well as safe pathways for both pedestrians and cyclists.

“I like the roundabout design. It makes sense for the future transportation that the city will be having,” McMullen said. “I would like for safe bicycle passage and pedestrian pathways to be very carefully thought about and studied. With traffic coming off of a major U.S. highway, safety is a great concern. I also ask that the design of the two circles be designed with art in mind.”

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