Wisconsin has more roundabouts than any other state. That's a good thing, experts say.

Did you know Wisconsin has more roundabouts than any other state in the union?

It's true, and to explain why the Milwaukee Journal Sentinel spoke with University of Wisconsin-Milwaukee professor of civil and environmental engineering Xiao Qin, who also explained why roundabouts have increasingly become popular, their safety benefits and the history behind them.

Qin is the director of the Institute for Physical Infrastructure and Transportation and the founder and director of the Safe and Smart Traffic Lab at UWM. In 2010 and 2011, he worked with the Wisconsin Department of Transportation on the first comprehensive safety evaluation of Wisconsin roundabouts during their first decade in the state.

How many roundabouts are there in Wisconsin?

There are currently 554 roundabouts in Wisconsin. Of these, 287 are on state highways and 267 are on local roads.

Most Wisconsin roundabouts are found in the eastern and southern regions of the state, in and around the Madison, Milwaukee, Green Bay, Oshkosh and Appleton areas.

A complete, interactive map of roundabout locations in the state, including proposed future locations, can be found on WisDOT's website.

What are the safety benefits of roundabouts?

Because roundabout traffic only travels in one direction, the possibilities of head-on collisions and left turn-related crashes are virtually eliminated, Qin said. These are two of the most severe and deadly types of collisions.

Additionally, the circular design of roundabouts is intended to slow drivers to speeds where crashes are far less severe. Most roundabouts have a posted speed limit of 15 or 20 mph. Even though minor sideswipes and "fender benders" can occur at these speeds, their consequences are generally far less severe than higher speed crashes, Qin explained.

Roundabouts are specifically designed to have fewer "conflict points" than other intersection types. The Federal Highway Administration, or FHWA, defines a conflict point as "any location where road users’ paths coincide, categorized as either crossing, merging, diverging or nonmotorized." The more conflict points at an intersection, the more unsafe it is, Qin said.

"The roundabout design reduces the number of conflict points at a conventional intersection from 32 to only eight," he said. "And for conflict points between pedestrians and motorists, roundabouts reduce the number of conflict points at the conventional intersection from 24 to only eight."

Although some studies point to roundabouts causing higher numbers of minor crashes ― a point which WisDOT recognizes in its manual ― Qin said, in terms of injury severity, roundabouts are considerably safer.

What city has the most roundabouts in the world?

With a roundabout at every 17 intersections, Carmel, Indiana, a suburb of Indianapolis, has more roundabouts than anywhere else in the world. It's one of only three U.S. cities that make the top 25 as of 2020. Berkeley, Calif., and Miami also make the list.

According to the Insurance Institute for Highway Safety, the average vehicle fatality rate per 100,000 people in the U.S. is 12.9. In Indianapolis, it's slightly higher at 14.2, but in Carmel, it's only 2.4.

What are other benefits of roundabouts?

Roundabouts don't only offer safety benefits. They're also better for the environment, make traffic more efficient and ultimately cost less to maintain than other intersection types, Qin said.

Drivers often just have to yield before entering a roundabout rather than coming to a complete stop, meaning fuel emissions are lower and less air pollution is created. Roundabouts can also serve as a space for landscaping and beautification projects, though, Qin said, for safety reasons, it is not recommended that stationary objects like statues are placed in the middle.

Roundabouts also cost less to maintain than other intersection types because they do not use traffic lights or electricity.

One traffic light costs about $400,000, Carmel Mayor James Brainard told CNBC earlier this year. An additional $8,000 to $10,000 per light, per year is needed for electricity and maintenance. Workers also must be paid to service, maintain and manage the timing of the lights.

Finally, roundabouts provide safety benefits to pedestrians and cyclists.

When a vehicle is entering or exiting a roundabout, it is easier for drivers to pay attention to pedestrians than at a conventional intersection because pedestrian crossings at roundabouts are not at the same place where vehicles are turning, Qin explained.

In contrast, at a conventional intersection, "sometimes, you are trying to make a right turn, and you only pay attention to vehicles coming from the left," Qin said. "Then, you may encroach into a crosswalk to your right side."

Are there any disadvantages of roundabouts?

Yes. While low posted speed limits are one of roundabouts' key safety measures, and roundabouts are even designed to slow speeding drivers down, their circular design can prove dangerous for some speeders.

"Not every driver sees speed advisories, so you will see an increase, potentially, in run-off-the-road crashes due to speeding, especially in bad weather or nighttime," Qin said.

Additionally, as mentioned above, studies have shown that minor crashes are more common in roundabouts than at other intersection types, often due to driver confusion or impatience.

And while roundabouts are designed for almost all traffic conditions, this doesn't mean they can be placed anywhere, Qin said.

Roundabouts are not ideal for areas with high volumes of heavy vehicle traffic ― vehicles such as buses, trucks, trailers and emergency vehicles. Although roundabouts are designed to safely accommodate these vehicles, heavy vehicles must take up both lanes of a two-lane roundabout in order to travel through. If an area's traffic is more than about 10% heavy vehicles, the area is not ideal for a roundabout, Qin said.

Roundabouts also do not typically work well in extremely busy areas because those with more than two lanes can become complicated and confusing for drivers, increasing collision likelihood. A 2007 National Cooperative Highway Research Program study found that motorists at multi-lane roundabouts are at least two times more likely to fail to yield to pedestrians than at single-lane roundabouts.

Building a roundabout in a busy, urban area can also disrupt the flow of traffic, Qin said. In these areas, traffic signals are often coordinated, so motorists traveling in the same direction along the same street all stop at the same time, even if they're stopping at different lights. Because roundabout traffic is not designed to come to a full stop, this can disrupt progression in coordinated traffic light systems.

What is a roundabout, and how do they work?

A roundabout is a type of one-way, circular intersection that has exploded in popularity in the United States and other countries throughout the 21st century due to its research-supported, safety-based design and other benefits.

WisDOT's Facilities Development Manual, which puts forth engineering and construction guidelines for roundabouts, states that a roundabout is defined by three basic principles:

1. Yield-at-Entry ― Vehicles approaching the roundabout must wait for a gap in the circulating flow of traffic, oryield, before entering the circle, because traffic already in the circle has the right of way.
2. Deflection ― Traffic entering the roundabout is directed or channeled to the right with a curved entrypath into the circulating roadway.
3. Geometric Curvature ― The radius of the circular road and the angles of entry are designed to slow thespeed of vehicles.

Most roundabouts have one or two lanes and are 80 to 120 feet in diameter, Qin said.

When were roundabouts invented?

Traffic circles have existed in Europe since the late 18th century, but it wasn't until the mid-20th century that the world's first modern roundabouts ― which engineers define as standardized roundabouts designed after 1960 to reduce speed and collisions ― were implemented in the United Kingdom.

According to the Federal Highway Administration, the first modern "yield-at-entry" roundabout was built in Britain in 1956. In 1966, "a nationwide yield-at-entry rule launched the modern roundabout revolution" in Britain. Roundabouts quickly became popular in Australia, and other "British-influenced countries" that drive on the left side of the road.

Countries that drive on the right side of the road were slower to adopt roundabouts, but they eventually erupted in popularity in the United States and western Europe in the 1980s and 1990s.

The first roundabout in the U.S. was built in the spring of 1990 in Summerlin, Nev., a "rapidly growing planned community" on the west side of Las Vegas, the FHWA wrote in 1995. The Summerlin roundabouts proved to be effective in safely managing the city's heavy traffic. Only four accidents were reported at the two roundabouts between their implementation in 1990 and the FHWA's report in 1995.

By the mid 1990s, roundabouts could be found in California, Colorado, Florida, Maryland, Nevada and Vermont.

How has the popularity of roundabouts increased Wisconsin over time?

Wisconsin's first roundabout was built in 1999 in the village of Howard near Green Bay. Qin said engineers were inspired by roundabouts' success in the UK, Australia and other U.S. states.

By the time Qin was studying roundabouts with WisDOT around 2010, the state had about 150 of them, he said.

Five years later, by the end of 2015, there were 350 roundabouts in Wisconsin, 149 of which were in the DOT's 11-county Northeast Region, where the Howard roundabout is located, said Randy Asman, a traffic engineer with the DOT's Northeast Region, in 2017.

"If you think about roundabouts as a stock price, you'd definitely want to buy it," Qin said. "It grew from (one in) 1999 to today's 554."