City proceeds with 27th St congestion remedies | PostIndependent.com

City proceeds with 27th St congestion remedies

A concept drawing showing a possible "mini roundabout" at the intersection of 27th Street and South Grand Avenue in Glenwood Springs
Rendering by SGM Engineers |

Glenwood Springs city officials are proceeding on two fronts, one short-term and the other a long-term solution, to correct problems that have led to peak-hour traffic congestion at the busy intersection of 27th Street and South Grand Avenue.

City Council tentatively agreed last week to move forward with more immediate plans to design and install what’s called a “mini roundabout” at the intersection that would allow the free flow of traffic in all directions.

That is, unless a split-phase traffic signal that would allow for left-hand turns onto South Grand while oncoming traffic is stopped proves more feasible and cost effective.

“I do see this as a temporary solution until we can rebuild the 27th Street bridge,” Mayor Mike Gamba said, adding he would like more information on the signal option before making a final decision.

Looking to the future, council at its May 5 meeting awarded a $1.2 million design contract to the engineering firm of AMEC Wheeler Foster for the eventual replacement of the 27th Street (Sunlight) bridge sometime after 2017 when the new Grand Avenue bridge is complete.

The 27th Street bridge has received federal design funding as a result of a low sufficiency rating due to the age and functionality of the existing two-lane structure.

A wider bridge that would include full turn lanes coming onto northbound Grand is envisioned as part of the city’s long-range transportation plan as a key component to reducing traffic congestion in the south Glenwood area.

Recently, due to traffic problems exacerbated by the start of construction on the Grand Avenue bridge, the city began disallowing left turns at 27th and S. Grand between the hours of 7-9 a.m. The move was meant to prevent long traffic backups over the bridge and up either side of Midland Avenue, especially during the morning student drop-off time at Sopris Elementary School.

While the turn prohibition addressed part of the problem, backups are now more frequent farther east at the intersection of Highway 82 and 27th Street where motorists wanting to head north on 82 now have to go during those hours, City Engineer Terri Partch said.

The city has asked if the Colorado Department of Transportation could allow for a longer turn signal at that equally busy intersection, but to no avail, she said.

As for the short-term fix, council will further discuss the options in June. But the mini roundabout has some advantages over signal options, Lee Barger of the city’s contract engineering firm SGM advised council.

Mini roundabouts are typically anywhere from 40 feet to 90 feet in diameter, as opposed to the 130- to 200-foot or larger full roundabouts, like the ones at 27th and Midland and in West Glenwood at Interstate 70 Exit 114, he said.

The smaller roundabouts are designed for speeds of between 15 and 20 mph, and have a traversable center island for larger vehicles to be able to navigate. That area can be delineated with paint or raised slightly with a split traffic lane circling to the outside.

Benefits, Barger said, are that they are more compact and efficient in keeping traffic moving while controlling speeds and maintaining safety. A mini roundabout can also be built for between $100,000 to $250,000, where a revamped traffic signal could cost significantly more, Barger said.

Some of the constraints, however, are that they can be confusing for motorists when larger vehicles have to cross over the center island, requiring some level of public awareness education before they can be implemented. They can also tend to increase the frequency of U-turns and are less efficient in moving traffic in a dominant direction, he explained.

That “could be a red flag” in analyzing the 27th and South Grand intersection for such a traffic control feature, he said.

Still, mini roundabout “have become a proven solution” in similar places around the country, Barger said.

A mini roundabout could also be implemented yet this year, where a major signalization change could take longer to implement, he said.

City Council is expected to revisit the issue and make a decision at its June 16 meeting.


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