Sioux Falls roundabouts irk some drivers, but city says they're working

Nikki Wallenstein doesn't like the latest trend in traffic engineering: roundabouts. Neither does her Ford Mustang.

Intended to keep traffic moving continuously by directing vehicles through a circular intersection, roundabouts have been popping up in Sioux Falls and other cities across the United States in recent years.

They're encouraged by federal government safety studies and are aimed at improved traffic flow, a reduction in accidents and less severity when accidents do occur.

But Wallenstein and a few others who've used the four roundabouts in the Sioux Falls area since the first was built nearly a decade ago haven't had the most positive experiences with them.

"People don’t understand the whole roundabout, it’s foreign to them," Wallenstein told the Argus Leader as she recounted an accident she was in at the 69th Street and Southeastern Avenue roundabout in summer 2017.

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Wallenstein was entering the roundabout from the north around 8 a.m. when another driver already in the circle struck the side of her "baby," as she described the 2007 Ford Mustang that suffered damage to its driver's side.

Since the roundabout was installed at that intersection in 2011, 14 accidents have occurred there. And based on analysis by the city of Sioux Falls' traffic engineering division, that's a slightly higher rate of crashes prior to the roundabout being built.

From 2005 to 2011, the crash frequency rate was 0.43 crashes for every million vehicles that passed through the intersection. Since then, the rate is 0.91 crashes for every million vehicles.

Heath Hoftiezer, principle traffic engineer with the city, said increased traffic caused by the growth of the southeast part of Sioux Falls led the city to replace the stop signs there with a roundabout in 2011. The other option was to put in a signalized intersection.

A roundabout was chosen for three reasons: It requires less maintenance than keeping stoplights working year-round; vehicles aren't forced to stop when there is little or no traffic; and crashes that occur at roundabouts tend to be less severe than those that occur at signalized intersections.

"There would be a lot more right angle crashes," Hofteizer said. "Most of these are just side swipes."

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The three other roundabouts in and near the city are proving effective, and safer than typical intersections.

Lincoln County opened its first roundabout last fall, and based on data provided by the county's highway department, no accidents have been reported since. In the four years prior, there were 15 crashes, or 1.2 crashes for every million vehicles that used the former four-way stop.

At Career Avenue at University Center, there have been zero accidents in the 11 years its been in use. And at the roundabout at Granite Lane and Granite Court near the Flying J Travel Center a few blocks away there's been one accident since it was installed in 2015.

Hofteizer said it's estimated the number of crashes wouldn't be much different if signalized intersections were installed in place of roundabouts.

"I would expect them to be at the same number," he said.

Wallenstein said a factor in her crash was the foliage that obstructed her ability to see to the other side of the roundabout and the other vehicle that was coming her way, a practice she believes makes roundabouts dangerous.

"There was a young kid going through there quite fast, and I couldn’t see him because of all stuff they put in there," she said.

Hofteizer admitted that the views are obstructed, and said that's been determined as a best practice designed to make roundabouts easier to use. Citing industry studies, he said crash rates at roundabouts where drivers can see the entirety of the intersection are higher.

"The crashes got worse… when it was completely open in the middle," he said. "People were looking at what was going on at the other approaches" and not focusing on their own.