CDOT: ‘Diverging diamond’ best option for Silverthorne |

CDOT: ‘Diverging diamond’ best option for Silverthorne

Caddie Nath
Summit Daily News
Denver Post

SILVERTHORNE – West of Great Britain, drivers are seldom encouraged to drive on the left side of the road.

But guiding drivers to the left for a brief stretch is a key component of the “diverging diamond” alignment transportation officials are proposing to improve traffic flows on the Interstate 70/Silverthorne interchange.

Unusual? Yes. Silverthorne’s diverging diamond could be the first of its kind in Colorado and one of only a handful in the U.S.

But it’s the least expensive improvement option for the beleaguered interchange and among the safest, Colorado Department of Transportation officials told the public at an open house on the project held in Silverthorne Wednesday night.

Approximately 30 people attended the meeting.

The diverging diamond would crisscross traffic below I-70, allowing vehicles to make an unimpeded left turn onto the highway.

It would cut costs by saving CDOT from having to reconstruct the existing bridges that carry I-70 over the interchange.

The diverging diamond was presented Wednesday as part of a package of improvements expected to cost $15-$19.5 million. Other interchange solutions could cost $30-$50 million, officials said at the open house.

Still, the project hasn’t landed state funding yet.

CDOT officials have pressed forward with studies and design plans for the I-70/Silverthorne interchange despite the lack of money, saying projects that are “shovel ready” tend to be first in line for funding when it becomes available.

“We have different funding scenarios that we continue to manipulate,” Kozinski said. “We look for projects that are ready to go.”

CDOT is currently working through the evaluation phase of the project, the first of three phases concluding with construction.

The interchange was determined to be in need of a makeover due to safety concerns, frequent backups that occur in the area on busy weekends and projected increases in capacity needs over the next two decades.

The diverging diamond is proposed in conjunction with other improvement projects, including a restructuring of the westbound on-ramp, making the grade less steep and widening the ramp to two lanes, as well as a project to increase capacity at the Highway 9 and Wildernest Road intersection to accommodate projected 2035 traffic conditions.

A less detailed study was also done on an eastbound auxiliary lane between Frisco and Silverthorne. CDOT recommended the extra lane be considered in the future.

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