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The 1990s gave Philadelphia a National League pennant. For the U.S., the start of the decade brought the country’s first modern roundabout, built just outside Las Vegas.

By 2000, when the federal government published its first roundabout “rule book”, there were fewer than 100 nationwide. But the number grew steadily. Today, there are over 10,000 across the country, according to the Philadelphia-based engineering consultant Kittelson & Associates, Inc.

Traffic safety data and experts say roundabouts are safer and more efficient than traditional intersections. The round shape slows traffic and creates a simpler flow, reducing the chance of serious accidents by eliminating complex turns and merging. Also, vehicles inside the roundabout have the right of way, helping traffic move smoothly.

Now, the Philadelphia area is expanding its network of roundabouts. The latest installment is the Penrose Roundabout in South Philly, which has replaced a large and complex signalized intersection at Moyamensing, Penrose and Packer avenues.

“The intersection was basically the size of Citizens Bank Park,” said John Boyle, research director for the Bicycle Coalition of Greater Philadelphia.

The Pennsylvania Department of Transportation plans to double its stock of roundabouts in the city and its surrounding suburbs from 28 to nearly 60 by 2029, according to department data shared with WHYY News. Chester and Bucks counties both account for more than two-thirds of the planned construction.

Boyle was impressed by the “quick build” of the temporary roundabout design at the outset of construction, which quickly changed the traffic pattern, he said.

“The reaction was immediate because people found that this crazy intersection [had] suddenly been tamed,” Boyle said.

The intersection is included in Philadelphia’s “High Injury Network” of dangerous roads — part of Vision Zero, the city’s effort to target streets with many traffic crashes.

The Penrose project is set to finish within its budget and six months ahead of schedule, said Christopher Young, communications manager of the Philadelphia Department of Streets, in a comment to WHYY News. Construction crews are finalizing pedestrian sidewalks and a separated bike lane before the spring ribbon cutting.

The $5.8 million contract — paid for by the state’s Automated Red Light Enforcement funds — was awarded to construction contractor JPC Group.

During construction, the city held three general meetings, where residents’ “fears were resolved,” said Barbara Capozzi, president of the nearby Packer Park Civic Association, in a comment to WHYY News.

“We all love it now. The traffic moves smoothly, neighbors report they feel like they are in Paris or London, and even the Uber drivers have gotten the hang of it,” Capozzi said.

Why a roundabout?

Slow speeds save lives.

If a car going 20 miles per hour hits a pedestrian, the pedestrian has a 90% chance of surviving, according to a Vision Zero report. That becomes a coin flip at 30 mph. At 40 mph, the chance to survive falls to just 10%.

When turning in a roundabout, drivers tend to slow down.

“It’s all about speed and response time,” said Jim Brainard, former mayor of Carmel, Indiana, known as the “roundabout capital of the world.” During his seven-term tenure, the Indianapolis suburb built 157 roundabouts and grew from 25,000 residents to a city of 100,000. It only has four traffic lights remaining.

Carmel is one of the safest places to drive in the country, with only two traffic fatalities for every 100,000 people annually. The national average is over six times that, at nearly 14 per 100,000. Philadelphia’s rate is seven per 100,000, according to the city’s 2024 Vision Zero Annual Report.

“I couldn’t take a roundabout out today if I wanted to,” said Brainard.

Local PennDOT data supports the safety argument. A September 2024 PennDOT study of converted intersections found that severe crashes dropped by more than half and overall crashes fell 7% after roundabouts were installed.

It’s not just about safety. Roundabouts can improve traffic efficiency up to 50% and can reduce gas usage and carbon emissions, given the lack of idling and need to electrify and replace traffic lights.

In Carmel, engineers built roundabouts on Range Line Road and, for a section, shrunk its five lanes to a single lane in either direction, maintaining or even reducing drivers’ commute times, Brainard said. With the extra space, a green median and a bike lane were built.

Point Breeze resident Michael Sievers, an administrative assistant at the University of Pennsylvania, said the former Penrose intersection was a “five-directional wasteland.” Sievers supports the construction of the roundabout, highlighting its efficiency.

“What used to be two-to-three-minute light, now you just zip right through it,” Sievers said.

Penrose also feels safer to walk through, according to Venus Lucini, 27, a casino dealer who has crossed the intersection with her young daughter before and after the redesign.

“It’s so much better now. You pretty much had to run, mostly because people used to not stop,” she said. “You had to wait until there was nobody and run as fast as you can. It was so dangerous before.”

Traffic safety doesn’t affect all Philadelphians equally. City zip codes with high rates of poverty see the highest rates of traffic crash hospitalizations, according to an analysis from the Philadelphia Department of Public Health.

Roundabouts are not traffic circles (or rotaries)

In short, roundabouts are smaller and there are no merging lanes. Traffic circles are larger, have signals and stop signs, and drivers often must stop for oncoming vehicles.

After becoming popularized in the early 20th century, traffic circles, or rotaries, became congested and dangerous as traffic volumes and vehicle speeds increased, eventually growing out of favor.

Meanwhile, in the 1960s, the United Kingdom came up with a simple fix to their own traffic circles, ushering in the age of the modern roundabout: Give the right of way to the traffic within the circle.

In the Northeast U.S., the common misconception between rotary and roundabout still persists, bringing anguish to drivers and affecting perceptions of modern roundabouts, said Rock Hoffman, news producer for Total Traffic & Weather Network in Bala Cynwyd.

“I think there’s a certain level of intimidation for drivers my age who remember those days of the circles through Cherry Hill, [New Jersey],” he said.

That intimidation grew to fierce backlash against an early PennDOT roundabout project in 2005, said Matthew Edmond, the Chester County Planning Commission’s executive director. The county is receiving at least 11 of the planned roundabouts.

“People [would] come up to [PennDOT engineers] and threaten them in person for putting these roundabouts in, because we literally had zero roundabouts in the region,” he said.

“It was brand new and all they knew were Jersey circles,” Edmond said, referencing one in Flemington, New Jersey, that some considered “hellacious.”

That said, once roundabouts started popping up, feelings quickly changed.

“Once they went through them themselves,” he added, “then all of a sudden it became a normal thing.”

Some critics of the Penrose Roundabout said it was too small and wondered if its redesign was money better spent on potholes.

Data suggests these critics may become supporters. A nationwide study found that the longer a roundabout is in place, the more supportive drivers become; around a third of drivers surveyed said they did not like roundabouts, but support jumped to over 50% after roundabouts were installed.

“Seeing is believing,” said Tim Garceau, urban planner and professor of geography at Central Connecticut State University.

Garceau said he found this pattern of acceptance mirrored at state transportation departments throughout the Northeast. Through interviews with dozens of officials, Garceau found that despite initial institutional reluctance toward roundabouts, eventually the data became overwhelming, and roundabouts were accepted as good design.

“They’re all on board,” Garceau said, in terms of now utilizing roundabouts. Some transportation departments, like New York’s, have gone as far as to implement a “roundabout–first” approach.

For Garceau, the initial, sometimes-harsh backlash to a proven traffic-calming solution goes back to something fundamental.

“For as rapid [a] change that we experience in our country, people are very averse to change,” he said.