Engineers have tweaked the design for a planned elevated roundabout at the southwestern Lincoln bottleneck of 14th Street, Old Cheney Road and Warlick Boulevard, providing drivers a better view of approaching traffic, beautifying the concrete walls and adding an underpass for cyclists and pedestrians on the Rock Island Trail.
Many people described the existing recreational trail crossing at Old Cheney Road as dangerous, and engineers were able to put in an underpass and stay within the construction budget, said Thomas Shafer of the city's Public Works and Utilities Department.
The new design should also help reduce the likelihood of flooding near the intersection.
More than 200 people attended the last of the public meetings on the intersection design this week. The focus of the next meeting will shift to construction schedules, as the city gets close to putting in the unusual intersection, a roundabout above a T.
The elevated roundabout design, selected following a design competition involving three firms, is intended to reduce congestion at the confluence of three streets without taking up a lot of additional land.
Engineers describe the intersection as a slightly elevated roundabout, like the first floor of a home with an above-ground basement.
City staff expect to begin utility work and right-of-way purchase in 2019, with construction scheduled for 2020 and 2021.
The project is expected to cost $30 million to $36 million, including $25 million in construction costs.
About 38,000 cars a day use the 14th and Old Cheney intersection, one of Lincoln’s busiest, and the new design will handle the traffic load of 59,000 cars expected by 2045, according to engineers.
Currently, Warlick Boulevard traffic intersects with Old Cheney traffic a few hundred feet from where Old Cheney meets 14th Street. Those intersections, and another at 16th and Old Cheney, are all controlled by traffic lights.
The new design, which includes a traditional roundabout on 14th Street at Brookridge Circle, will reduce the so-called vehicle conflict points, locations in the area where an accident can occur, from 80 to 39, according to Shafer.
And the new intersection has a 6-to-1 cost-to-benefit ratio, which is "off the charts," said Steve Wolf, with JEO Consulting Group Inc. That ratio, which incorporates the economic benefits of the improvements, will only improve when safety considerations are added to the equation, he said.
Drivers will be able to use either the roundabout or the ground-level T intersection for most movements. However, the roundabout cannot be used to go east on Old Cheney and the T intersection cannot be used to go south on 14th.