Welcome, everyone, to the summer when America tries to figure out what exactly it is going to do with these electrified mountain bikes.

Out in Marin County, California — the nation's cradle of mountain biking — citizen advisory committees have been empaneled, trying to decide where electric mountain bikes, aka eMTBs, should be allowed to roam. This summer, Boulder, Colo., is in an official "pilot period" to see what is happening with eMTBs in open public spaces. Massachusetts is convening hearings on a proposal to ban all eMTBs on any natural surface trail, including singletracks, managed by that state.

How about, say, Minneapolis?

"We are trying to figure out if (eMTBs) will be allowed," said Robin Smothers, a spokeswoman for the city's Park and Recreation Board, which oversees 8 busy miles of trails in Theodore Wirth Regional Park. "It's a timely question right now."

Timely because sales of all kinds e-bikes are exploding, and eMTBs are a special kind of beast. They are, by all accounts, loads of fun, with an e-boost that allows riders to scamper up hills. And like all e-bikes, they are extolled as the new best friends of growing legions of geezer riders.

The problem — the reason the trail management world is abuzz with eMTB policy development — is that eMTBs are heavy (often more than 45 pounds), fast (the least powerful models can top out at 20 miles per hour), and the e-boost's additional torque has in some locations torn up trails in ways that pedal-only bikes could not.

That tension — potential opportunity vs. potential mayhem — is reflected policies of the International Mountain Biking Association, the 30-year-old mountain bike advocacy group. Its policy is that "electric mountain bikes (eMTBs) present opportunity and challenge to traditional mountain bike access. If managed effectively, eMTBs may increase ridership and stewardship of trails. No management, poor management and misinformation, however, have the potential to jeopardize current and future access that mountain bikers, local organizations and IMBA have pursued for the past 30 years."

The association has endorsed use of the least-powered eMTBs (called Class 1 bikes) as long as the trail's management is certain that the e-bikes "will not cause any loss of access to nonmotorized bikes" and trail conditions are sustainable.

That essentially is where the Three Rivers Park District has landed for its 36 miles of single track trails. As long as an eMTB has working pedals, can't go faster than 20 mph with pedal power, and that power disengages when the bike's brakes are applied, the district is OK with it.

Minneapolis, meanwhile, has no such restrictions at the moment. The park board has ambitions to "remove the ambiguity out on the trails," said Tyler Pederson, a parks and recreation design project manager, but has no precise schedule to do so.

"But it is something we have to do," Pederson said. "This could affect trails. And most of our trails are maintained by volunteers and donations. We have to remember that."

Has Pederson riden an eMTB?

"They're fun," he said. "But on the one I rode, the power definitely didn't disengage when I put on the brakes. Those bikes are out there. It's not a big issue yet. Yet."

Look out! It's a scooter!

Another summer trend watch: Are e-scooters about to overtake bicycles as the most injury-prone way to bomb around town?

This question comes from the Journal of the American Medical Association, which recently reported that in a one-year study of Los Angeles emergency rooms, injuries while riding stand-up electric scooters exceed those of people riding bikes or just walking. The count was 249 people with scooter-related injuries (70% of which involved either fractures or head injuries); 195 cases of bike-related injuries; and 181 injured pedestrians.

That intense bit of analysis has been difficult to replicate in the Twin Cities, but it's on the way. The Hennepin County Medical Center has seen enough new variety to the contraptions on which its emergency patients have been hurt that it is reviewing the way it categorizes injuries. Now, apparently, e-scooter injuries can get lumped with even those from motorcycles.

"We have had five cases that may be attributed to e-scooters since 2018," said Hennepin Healthcare spokeswoman Christine Hill, "but I suspect that number is higher."

Tony Brown is a freelance writer from Minneapolis. His column appears twice a month. Reach him at mplsbikeguy@gmail.com. Read archived columns at startribune.com/bikeguy.