Cranberry Township's fondness for roundabouts isn't unique to southwestern Butler County.

And while safety is the No. 1 priority, Cranberry boasts of numerous benefits provided by the circular junctions.

Kelly Maurer, township public works director, said the draw to roundabouts is a state transportation department inclination, not one simply drawn up by Cranberry traffic planners.

“PennDOT encourages their use,” Maurer said. “Whenever a traffic signal is warranted at a new location, you consider a roundabout if it's feasible at that location. There's several reasons for that.”

The township already touted the safety factor provided by roundabouts — a PennDOT study of 26 roundabouts statewide, including one in Cranberry, found a 22% drop in crashes, 36% decrease in minor injuries, 81% decline in serious injuries and 100% fall in fatalities at those intersections compared with the intersections before roundabouts — but Maurer said there are several additional pros.

Perhaps, the most counterintuitive, given the slow speeds within traffic circles, is that roundabouts increase the flow of traffic.

“They have increased capacity,” Maurer said. “They can typically move roughly 30% more vehicles than a signalized intersection.”

That's because, in a roundabout, vehicles are always moving, unlike at a junction with four traffic lights.

In non-peak traffic — 11 p.m., for instance — a car can ordinarily approach, drive through and exit a roundabout without having to stop, while the same may not be true at a signalized intersection.

During peak traffic, while some cars may have to yield to traffic already in the circle, motorists on average will wait less than they would at a traffic light.

“It slows everybody down, so everyone has a chance to safely enter that intersection,” Maurer said.

That movement, in addition to increasing the flow of traffic and decreasing the likelihood of crashes, also has an environmental impact, Maurer noted: There's no long queue of vehicles idling at a red light.

It also has additional, although indirect, environmental benefits — ones that also reduce the number of tax dollars spent on intersection upkeep.

“There's less long-term maintenance,” Maurer said. “Once the roundabout is built, there's some landscaping,” but no electrical usage or traffic light replacement.

In terms of safety, roundabouts — in addition to decreasing the likelihood of fatal car-on-car collisions — provide pedestrians and bicycle traffic with more places of refuge.

The PennDOT study showed a decline in crashes involving non-vehicular traffic at roundabouts, and Maurer said there are two main reasons.

The first, Maurer said, is the same as with every other benefit: Vehicles are moving more slowly, so there's less of a risk of a speeding truck running a red light into a crosswalk.

Second, while a roundabout introduces more places for pedestrians to cross, that actually decreases the likelihood of a car-on-pedestrian accident, Maurer said.

“They have safe refuge,” Maurer said. “Normally, they don't have to cross multiple lanes of traffic; they have a median in the middle.”

Four roundabout projects are in planning or in construction in Cranberry, including the anticipated MSA Thruway project, which includes two rotaries on either side of the tunnel under Route 228.Another project is the construction of a roundabout outside of Ehrman Crest, Seneca Valley School District's future new elementary and middle school on Ehrman Road.“The township was very much in favor of a roundabout there, due to the pedestrians walking to school, the buses,” Maurer said. “It would be a safer environment for everyone.”Rounding out the round intersections are a traffic circle behind the Meeder development as well as one that will connect Brandt and Executive drives.Maurer said the township's long-term traffic planning also includes the evaluation of other intersections — such as some on Franklin and Rowan roads — for an upgrade to a traffic circle.But outside the four projects in planning or construction, Cranberry has no immediate goals of rounding out its junctions.