Whether a fad or for-keeps, the electric scooter craze has taken firm hold in the Twin Cities, with more than 4,000 scooters expected to hit the streets this summer — double the number from last year.

The anticipated surge has raised concerns about safety.

Dr. Andrew Zinkel, an emergency room doctor at Regions Hospital in St. Paul, saw an uptick in scooter-related injuries after their introduction last summer.

“I would say 99 percent [of the patients] weren’t wearing helmets,” said Zinkel, who heads the Minnesota chapter of the American College of Emergency Physicians. “Most people using scooters aren’t really planning in advance, so they’re not walking around with a helmet.”

Helmets aren’t required by Minnesota law, or by Minneapolis or St. Paul ordinances. But cities and scooter companies recommend them.

Doctors at HCMC in downtown Minneapolis, a popular area for scooting, saw “very few” scooter-related injuries last summer, according to spokeswoman Christine Hill. But she noted that it was hard to get an accurate number, because injuries may have been logged using different medical insurance codes.

This month, two people in California died in scooter-related crashes. And the Centers for Disease Control and Prevention in Atlanta announced a probe this month exploring the increase in scooter-related injuries in Austin, Texas, much in the same way it would study a disease outbreak.

At the behest of Austin’s Public Health Department, the study will “ask some very basic questions about injuries related to dockless scooter use,” said spokeswoman Linda Cox. Results and recommendations are expected later this spring.

A study of 249 patients with scooter injuries was released in January by researchers at UCLA in Southern California, the national epicenter of scooter use. Head injuries, fractures, cuts, sprains and bruises were treated by emergency room doctors most frequently, the study found. Ninety-two percent of those injured were operating scooters. Only 4 percent were wearing a helmet.

California-based Lime said it is using “innovative” technology, infrastructure and education to “set the standard for micromobility safety.” This includes partnering with the “industry, the medical community and regulators to create a meaningful ecosystem for this new and evolving technology.”

Lime has launched a next-generation scooter with “upgraded wheels, better suspension, additional braking and improved balance.” California’s Bird also has launched a beefier scooter.

Paul Steely White, Bird’s director of safety policy and advocacy, said the company’s research has found that “e-scooters and bicycles have similar risks and vulnerabilities.” The company continues to push for more protected lanes for bikes and scooters in communities where it operates, he said.

Both companies have invested in scooter safety awareness — Lime said it spent $3 million for its Respect the Ride campaign about “safe and responsible riding.” Bird last year formed a Global Safety Advisory Board led by David Strickland, head of the National Highway Traffic Safety Administration during the Obama administration.

Safety education will be an important factor as officials in Minneapolis and St. Paul decide on scooter vendors. Each city expects to introduce up to 2,000 scooters later this spring. More than 280,000 scooter trips were logged in Minneapolis and St. Paul for an abbreviated period last summer.

The trend is cheered by those pushing alternative modes of transportation.

“People like them, they’re convenient and they’re a great way to get around the city for shorter trips,” said Reuben Collins, a transportation planner and engineer for St. Paul. “We didn’t hear any concerns last year that would lead us to not have scooters back.”

The cities also hope to educate people about road etiquette — no riding on sidewalks, for instance. Minneapolis encourages people to contact its 311 helpline with scooter feedback.

Though scooters appeared with little notice last summer, Minneapolis embraced them. “We saw it differently than a lot of cities,” said Joshua Johnson, the city’s advanced mobility manager. “It wasn’t a threat. We wanted to harness it and achieve the potential we saw.”

Meanwhile, scooter-related injury litigation is an emerging area of the law, said Andrew Rorvig, a Bloomington attorney, and personal injury lawyers are taking note. “There’s bound to be a tragic situation where someone on a motorized foot scooter blows a red light, or is riding on the sidewalk down Grand Avenue in St. Paul and causes a bad injury,” he said. “Someone will ask, ‘What’s my remedy?’ ”