‘Double diamond’ idea gets favorable reception

By Corene Brisendine

Several Manhattan residents told engineers Wednesday that the “double diamond” proposal is a workable solution to congestion at the intersection of Seth Child Road and Fort Riley Boulevard.

Chuck Bartlett, project manager for Alfred Benesch and Company, said several people at the meeting liked the proposed changes, but were wary about the function of it once in place. He said although the interchange looks complicated from the aerial view, when someone drives it, the switching lanes are not “even noticeable.”

The “double diamond” format involves installation of two traffic lights on Seth Child Road, one at the ramps north of Fort Riley Boulevard and a second at the ramps south of Fort Riley Boulevard. Each set of lights would be used to switch the flow of traffic to the opposite sides of the road, eliminating the need to cross traffic for left turns through the interchange. The cost is estimated at about $1.3 million.

Bartlett said the double diamond configuration was the best solution to handling “large left turning volumes” because it eliminated the need to cross traffic to make the turn.

Local residents did voice concern for pedestrian and bicycle traffic through the intersection. Bartlett said although the city had not contracted his firm to design the intersection, the best way to get foot traffic through the interchange safely would be to funnel it to the center of the diamond and then back out, using the traffic signals as safe crossing zones.

Other residents said they wanted to know whether the city would look into several problems on Allison Avenue, Stagg Hill Road and Rosencutter Road near the interchange. Citizens asked whether the stop sign at Seth Child Road and Allison will be replaced with traffic signals. Peter Clark, city traffic engineer, said doing so would be irresponsible because the steep hill to the west of the intersection gives motorists problems when the roads become snow and ice packed. He said the city would have to do something to the intersection to allow enough room for people to stop before installing traffic signals. Clark also said the city will need to address the other intersections later, noting that the $900,000 Kansas Department of Transportation grant was to only address congestion at the Seth Child interchange. But he said the information from the study did show other intersections needed to be fixed.

Rob Ott, city engineer, said he was happy that people were “getting excited” about the Rosencutter Road/Richards Drive intersection. He said he is working with KDOT to build new bridges across Wildcat Creek on Fort Riley Boulevard east of the Rosencutter intersection, and staff at KDOT told him they want the bridges to last at least 75 years. Ott said in order to make that happen, they may need to widen the bridges to accommodate at least six lanes of traffic instead of the current four lanes, and they may also need to raise the bridge to allow for future water flows. He said the public consensus against a prohibition on left turns at Rosencutter/Fort Riley Boulevard helps with the future intersection’s design and the bridges’ design. He said KDOT plans to begin designing the bridges in 2014, and construction should begin in 2017.

Clark said the city should begin designing the Seth Child/ Fort Riley Boulevard intersection in 2014 as well. He said he plans to take the proposed intersection and study results to the August 6 city commission meeting, where commissioners will either approve or deny moving forward with the project. If the project moves forward, KDOT will release the $860,000 left in the grant for construction in 2015.

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