Party bikes, both loved and loathed, are back for the summer. But how safe are they?

Fifteen people were riding on an open-sided pedal pub in Atlanta on a warm Saturday evening when it rounded a corner and tipped over, slamming to a stop after hitting a tree along a median.

Distraught passengers and bystanders at a nearby café rushed to lift the carriage off people stuck underneath, according to a surveillance video released by police. Two people were critically injured, three were in serious condition, and the 10 others reported minor injuries.

"They were coming really fast ... and then spilled over," a witness can be heard telling 911 dispatchers in audio released by the Atlanta Police Department, who charged the driver with a DUI.

The April crash renewed attention to the mobile bike trolley bars, whose loved and loathed presence has expanded widely to dozens of U.S. cities – despite now being largely banned in the European city where they originated. The growing industry of carriages that are not-quite-bike, not-quite-vehicle has created regulation hurdles and resulted in at least occasional reports of injuries or accidents.

"The more you see these things popping up in downtown areas, urban areas, we're going to see more" accidents, said Page Pate, an Atlanta attorney with experience in civil and criminal litigation but who is not connected to the crash.

Despite such safety concerns, data on the pedal carriages isn't tracked by federal agencies that collect such statistics for traditional bicycles and automobiles. Authorities in Nashville, Tennessee, for example, where dozens of pedal pubs operate, say they have a safe track record. Police in Atlanta told local media they knew of no other such accidents.

Pedal Pub, a Minnesota-based company that says it operates in more than 50 cities with more than 60 franchised and licensed locations in the U.S. and Canada that serve more than 500,000 riders each year, said in a statement that serious injuries are rare.

"In our 15 years and over 5 million riders, we are aware of only three accidents that resulted in serious injuries, including the recent incident in Atlanta," Todd Treml, president of Pedal Pub Development, told USA TODAY in the statement.

Owners of party bike businesses say they use waivers and give safety briefings, requiring passengers not to jump off or stand up during rides, while drivers monitor passengers for signs they are drinking too much.

"It's definitely something we have to keep an eye on because obviously, we want everybody to be safe," said Andrew Beaston, who runs a pedal tavern in Ottawa, Ohio.

PARTY BIKE CRASH: 15 people injured after pedal pub in Atlanta overturns

Legions of pedal pub riders each year

Pedal bikes, party bikes, pedal pubs, pedal taverns, pubmobiles: They go by many names and take a variety of forms. Some are not motorized and require a certain number of passengers to move the vehicle. Others are motorized or have electric power to assist peddlers.

For example, Pedal Pub's "North American bike with the barrel" features an outer ring of seats for patrons to sit on and face inward, toward the driver, while pedaling. Pedal Pub promotes the experience as "a chance to socialize with friends, partake in a light workout, and tour neighborhoods and cities in an exciting, unique way."

According to Pedal Pub, the world's first party bike was developed and built in 1996 by brothers Zwier and Henk Van Laar in the Netherlands, and manufacturer Fietscafe made "the original party bike." The company says it "brought the first party bike from Amsterdam" to the U.S. in 2007, in Minneapolis.

Pedal Pub in Atlanta allows people to ride along a route and stop at bars and restaurants, according to its website. Riders are allowed to bring beer and wine on the pedal pubs, but they cannot bring liquor or take drinks off the ride.

The carriages, often full of boisterous revelers, have inspired legions of both fans and critics, including Facebook pages such as "I HATE the Pedal Pub." While some cities such as Naperville, Illinois, have blocked them from operating, others have embraced them.

"Can I say AMAZING!? My friends and I was celebrating a bachelorette party," one client wrote of Atlanta’s Pedal Pub on TripAdvisor. "Our guide was THEE BEST and his playlist was the bomb! I do not remember his name because I had one too many drinks lol."

In Nashville, the roughly two dozen pedal pubs operating at any one time divide opinion between "the bachelorette parties who love them and the commuters stuck behind them who loathe them," according to the online publication Sounds like Nashville.

The vast majority of reviews rave about the experience but a few don't. "It seems like a good idea: cardio AND drinking. You get on the pedal tavern, you get into traffic. You drink/pump/listen to music – and get flashed the middle finger by 1 out of 3 to 5 drivers. Some glare, some honk. Some pull up dangerously close," a reviewer on TripAdvisor wrote about a party bike ride.

Party bikes 'exist in a gray area'

It's unclear how often bicycle bars are involved in accidents or injuries. The National Highway Traffic Safety Administration, the U.S. Consumer Product Safety Commission and the National Safety Council all said they did not track data on the pedal bars.

The lack of data is partly because they "kind of exist in a gray area," said Christian Stefanut, a wholesale insurance broker with Michigan-based Burns & Wilcox who works with retail agents and has helped obtain insurance policies for such pedal carriages.

In part, because riders aren’t enclosed in a vehicle frame, Stefanut said insurance claims from auto collisions or someone falling off can be costly when they do happen. That has helped make some insurers more reluctant to underwrite policies, he said.

"Five or six years ago, we were writing (policies) at $3,500 each. And now they're closer to $25,000 or $35,000" per year per pedal pub, he said.

In 2013 in Minneapolis, 10 people were injured and two hospitalized after a party bike tipped over, according to local news reports. Two years later in the same city, 12 people were taken to the hospital – three with serious injuries – after a party bike was read-ended and tipped over, local reports said.

In 2017, a woman sued a Nashville pedal bar company alleging she suffered "serious, disabling, painful and permanent bodily injuries" on a ride. The woman alleged the bike blasted music so loud that the driver could not hear panicked screams when her foot slipped off of her pedal and slammed against the pavement.

In 2018, a party bike in Memphis, Tennessee, had just let off a dozen or so passengers when a street trolley slammed into the rolling tavern. The trolley driver was taken to the hospital.

'WHY CAN'T WE ALL GET ALONG?' Party bike owner asks after trolley collides with bike

That same year, a woman riding a pedal pub that crashed into another quadricycle in Detroit sued the operator after suffering a fractured skull, according to the complaint.

Owners of several party bike companies told USA TODAY they take various steps to promote safety.

Pedal Pub Development "invests in extensive upfront safety precautions for independently owned and operated Pedal Pub franchisees before they are even open – from hands-on pilot field training to regular bike inspections to yearly national pilot recertification for our 21 plus year old pilots," Treml said.

Breton Smith, who runs a Miami pedal pub business, said party bikes are safe, "as long as everybody's playing their part." That includes making sure the driver is well-trained and riders understand rules, such as not jumping off midride.

Pate, the Atlanta attorney, said the party bikes contain inherent risks. Most riders sign waivers but that doesn't fully protect operators from liability, he said.

"It's a problem that's waiting to blossom. I think, unfortunately," he added.

Regulations, ‘rowdy behavior’ bring challenges

The pedal pubs have also posed regulation challenges for cities and states.

Some states have had to seek to change laws just to license them. One Rhode Island man bought a pub from China only to find out it was too large to be considered a bicycle and too slow to qualify as a motor vehicle.

Other states such as Michigan changed laws to allow passengers to have open containers of alcohol on board. Cities have also had to adopt regulations and licensing rules.

Amsterdam, the home of the party bike, banned "beer bikes" in 2017 when its District Court ruled the city "experienced a lot of nuisance in recent years caused by drivers of beer bikes." The court said the industry "easily leads to rowdy behavior and nuisance" and creates traffic problems.

The ruling came after about 6,000 locals signed a petition calling on the council to ban the bikes, according to the BBC.

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In Nashville, complaints about pedal pubs have been largely drowned out by the proliferation of motorized, open-air party vehicles. A push for stricter regulations ramped up last July after a man was injured after falling off a party bus and was run over.

"They are loud. They slow traffic. They're not safe. And the behavior has just escalated to an unacceptable level," said Butch Spyridon, president and CEO of Nashville Convention & Visitors Corp., of the larger party vehicle boom. "You have a moving vehicle and significant consumption of alcohol. It's a recipe for disaster."

Party bikes in Nashville were already subject to regulations, including background checks for drivers, insurance and equipment safety. They have posted a "good safety record" with no reported patron injuries requiring hospitalizations, said Billy Fields, director of the city’s Transportation Licensing Commission.

Michael Winters, who owns the party vehicle business Nashville Tractor and is also the head of the Nashville Transportainment Association, said accidents in party vehicles of all stripes are rare for an industry that in Nashville gives nearly 2 million rides a year.

Spyridon acknowledged that, in Nashville, pedal bikes are now "the calmer of all of them." He said he's not against fun, but they still can fuel unruly behavior.

"The music’s loud. The hollering is loud. It’s a license to behave like it's Mardi Gras," he said.

To many riders, that's exactly what makes them fun.

Contributing: Patrick Anderson, The Providence Journal; Natalie Neysa Alund, Nashville Tennessean.

Follow Chris Kenning on Twitter at @chris_kenning. Grace Hauck can be reached at ghauck@usatoday.com or @grace_hauck.

This article originally appeared on USA TODAY: Party bikes, pedal pubs: After Atlanta accident, how safe are they?