About five months after city commissioners used a set of studies to justify the approval of a new dual lane roundabout along a busy West Lawrence street, neighbors are presenting studies that suggest such roundabouts increase the likelihood of bicyclists being involved in accidents.

But city commissioners declined to reopen debate on the project at their Tuesday evening meeting, and engineers said construction work on the project is scheduled to begin by mid-to-late summer.

The roundabout is planned for the intersection of Wakarusa Drive and Inverness/Legends Drive. It is scheduled to be the city’s first dual-lane roundabout.

The roundabout proposal sparked multiple negative comments from neighbors in November when commissioners considered the project. But on a 4-1 vote, commissioners approved the project, in part because city engineers presented data from several studies suggesting roundabouts improved both motorist and pedestrian safety.

Over the last several weeks, however, neighbors near the intersection have been doing their own research, and said city engineers didn’t mention several contrary studies, including one that suggested bicyclists were at a greater risk for an injury accident in a dual lane roundabout.

Colin Howat, an engineer who lives near the intersection, wrote that the published studies he read are far from conclusive on whether dual-lane roundabouts make intersections safer. He cited one, 2013 Florida study, that indicated cyclist were at a greater risk of casualty accidents in roundabouts, particularly in dual lanes.

“I can only conclude the ‘first, do no harm’ mantra has not been invoked and this proposal is a costly answer in search of an unknown question,” Howat wrote in a recent letter to commissioners.

City engineers conceded there are studies that have indicated an increase in cyclist accidents. But Chuck Soules, director of public works, said he doesn’t think the design of roundabouts are necessarily causing more accidents, but rather cyclists haven’t yet learned that they should take the entire lane of a roundabout when using it, rather than sharing it with a motorist.

Soules said he is still confident that a dual lane roundabout will improve safety at the intersection, especially when you account for motorists, pedestrians and cyclists.

“Accidents will occur with a roundabout, however, due to slower speeds and fewer conflict points, there should be fewer accidents with less severity,” Soules wrote in a memo to commissioners.

Mayor Mike Amyx — who was the lone vote against the project in November– asked commissioners on Tuesday whether they wanted to reopen the debate on the roundabout, given the new concerns from neighbors.

None of the commissioners made a motion to reconsider the discussion.

“I don’t see enough information that I want to revisit it,” Commissioner Terry Riordan said. “I see some important points, some good points, but I don’t see it rising to the level of changing the decision.”

In other news, commissioners deferred until May 6 a decision on whether to establish a no parking zone along a portion of Hilltop Drive near Hillcrest Elementary School. Neighbors were divided on the recommendation to establish the no parking zone, and commissioners said they wanted more information from the school district.