Since 2007, seven “roundabouts” have opened around the periphery of Ann Arbor, mostly at intersections previously controlled by stoplights. Planners promised they’d yield less congestion and fewer accidents. Have they?
“They do help keep the traffic flowing,” says Seto. In an email, Jamie Adkins, the AAPD officer monitoring the roundabouts, adds: “There does not seem to be the back-up in traffic during high volume hours at the busier intersections [like] Geddes/Earhart and State/Ellsworth.”
“The observation after construction shows there are no delays,” confirms Les Sipowski, the city’s senior project manager in charge of roundabouts, in an email. “We hear no complaints from the travelling public. In fact we do not hear any complaints on delays on any of the roundabouts, even the most complex one at Ellsworth and State.”
How they affect the accident rate isn’t so clear-cut. Unlike at stoplights, traffic in the circles moves continuously, and some drivers misunderstand or misjudge when it’s safe to enter.
“In general we see some reduction of crashes [after roundabouts are installed],” says Sipowski. “But what is more important is there is a significant reduction in injury crashes.”
The city opened its second roundabout, at Huron Parkway at Nixon, in June 2009, replacing a four-way stop. The intersection qualified for a traffic signal, Sipowski writes, but “the city decided to see if a roundabout [was] not a better option.”
It seems to be. Adkins reports better flow there, and while police records show fifteen crashes near the intersection from 2011 through 2013, Adkins writes that there’ve been “no crashes reported” within the roundabout in the last four years.
That’s a relatively low-traffic intersection, as is the one at Skyline High. The circle built by the city at Geddes and Earhart, and two adjacent ones built by MDOT at the US-23 ramps, are much busier. Records show thirty-six crashes in the vicinity of those roundabouts from 2011 through 2013, or an average of a dozen a year; of those, Adkins writes, about one-quarter occurred in the roundabouts themselves.
The Washtenaw County Road Commission opened the city’s newest and busiest roundabout last October at the heavily traveled and infamously congestion-prone intersection of Ellsworth and State. The Ann Arbor and Pittsfield Township police departments share responsibility for the intersection, and their records show that right after the roundabout opened, crashes increased dramatically: The Ellsworth and State intersection averaged 27.5 crashes a year in 2011 and 2012, and recorded twenty-six last year through September–but there were forty-eight more in 2013 after the massive two-lane roundabout opened in October. Things improved somewhat this year, but with forty-four reports through May, the accident rate is still much higher than it was before the roundabout was built.
As promised by advocates, it does appear that the accidents are less severe. Instead of inattentive drivers plowing into cars backed up at the traffic light, drivers are more likely to hit one another at an angle, or sideswipe other cars within the roundabout. Of the forty-six accidents the AAPD responded to in the thirty-three months before the roundabout opened, thirty-three were classified as “rear end,” nine as “sideswipes,” three as “angle” and one as “other.” By comparison, of thirty-five crashes reported to the AAPD after the roundabout opened, only eight were classified as “rear end,” eighteen were the less serious “angle,” seven were sideswipes, and two were “other.”
“There is definitely a learning curve to driving a roundabout,” concludes Sipowski. But he believes the worst is already over: “We have anecdotal evidence [that] there are less people stopping within a roundabout, and less people waiting for the traffic to clear on all approaches before they enter the roundabout.”
