CARBONDALE, Colorado - Rather than the two-lane roundabout proposed by the Colorado Department of Transportation (CDOT) for the intersection of Main Street and Highway 133, a one-lane roundabout may be able to handle the traffic volumes projected there in 20 years.
That's according to an independent analysis of roundabout possibilities by the Walkable Livable Communities Institute, a Washington-based group commissioned by the town of Carbondale to study alternatives to CDOT's proposed roundabout design.
Carbondale trustees discussed those possibilities at their meeting Tuesday night.
Michael Wallworth, an analyst who completed the study on behalf of the town, proposed in a memo to the town that CDOT build either a one-lane "radial" roundabout or a two-lane roundabout, the outside lane of which could be covered by temporary curbs until traffic increased enough to warrant its use.
By 2032, CDOT projects that the intersection in question could see peak traffic volumes of up to 1,900 vehicles per hour in the morning and 2,200 vehicles during evening rush hour.
Still, Wallworth wrote that a two-lane roundabout wouldn't necessarily be needed to accommodate that traffic, and a smaller option could "fully address the needs of all modes of transportation, and hence potential for added safety, while accommodating needed capacity."
A one-lane roundabout wouldn't require added traffic signals, Wallworth noted, which would reduce driver delays compared to the so-called "offset left" option proposed by CDOT.
That option tends to encourage high speed exit from the roundabout, Wallworth wrote, as well as high speed right turns that can endanger pedestrians.
Trustees Allyn Harvey and Pam Zentmeyer both reiterated their support for a one-lane roundabout option, but Terry Kirk, the owner of Sopris Liquor and Wine in Carbondale, cautioned town officials to be sure they don't "underbuild" the roundabout only to have to expand it again when traffic increases.
"It's going to be a long construction period," he said. "We don't want to put local businesses through more than we have to."
The roundabout is proposed as part of $4.4 million in improvements that CDOT has planned for the Highway 133 corridor.
Construction on the project is expected to begin in 2014, and Carbondale Public Works Director Larry Ballenger said the design should be completed by the end of this year.
CDOT engineer Roland Wagner, who is performing a "peer review" of the roundabout options, could not be reached for comment. He will be back before the Carbondale trustees in the coming weeks to discuss his findings.
In other news, the trustees:
• Directed town staff to continue research into makers of a so-called "screw press" technology that could transform the town's sewage sludge into a "cake" product that is drier, easier to handle and cheaper to transport. Cooper Best of SGM Engineering, who produced a study for the city on the new technology, said it could reduce sludge-related truck trips from 350 to between 70 and 80 per year.
• Approved a letter of intent to participate in a solar energy power purchase agreement with Sunsense Solar, a Carbondale-based energy contractor. The agreement would involve installing solar panels on several town-owned facilities, possibly including the town shop, the water treatment plant, the Third Street Center and Town Hall.
• Awarded a contract for $47,110 to Highland Landscape of Carbondale for the installation of an irrigation system in a new town-owned community garden, to be located near the south side of the Third Street Center in Carbondale.
• Passed a resolution in support of a $109,000 grant application that the town submitted to Great Outdoors Colorado (GOCO) for the construction of a bike park at the North Face Park site in Carbondale. The town has pledged a $10,000 matching grant for the project, and Alpine Bank and the Thrift Shop of Aspen have also pledged their support if the town receives the GOCO grant.