WASHINGTON — Motorized electric bicycles may soon be humming along serene trails in national parks and other public lands nationwide. It’s part of a new Trump administration order — hotly opposed by many outdoors groups — that will allow e-bikes on every federal trail where a regular bike can go.

Sales of the bikes, powered by both pedals and battery-driven small motors, are booming, and some aging or less fit people have sought the rule change. It will allow them to whir up and down biking trails in the country’s roughly 400 national parks and other federally managed backcountry areas.

Interior Secretary David Bernhardt signed the order without fanfare Thursday, classifying e-bikes as nonmotorized bikes.

The e-bikes “make bicycle travel easier and more efficient, and they provide an option for people who want to ride a bicycle but might not otherwise do so because of physical fitness, age, disability or convenience,” National Park Service Deputy Director P. Daniel Smith said in a statement Friday.

Welcoming the change in Bar Harbor, Maine, on Friday, Gordon Goodwin, 69, said he and his wife look forward to riding the 57 miles of carriage paths that meander throughout Acadia National Park.

The paths, offering stunning views of lakes, mountains, forests and the ocean, are popular with bicyclists, but e-bikes have had to stay on the park’s roads instead.

“We’re stoked. We’re really stoked,” Goodwin said. “There’s just too much traffic on the main park roads that you can’t enjoy them. It’ll be great to get in the park and see nature and all that stuff.”

But more than 50 hiking, horse-riding and other outdoor and conservation associations, including the Appalachian Trail Conservancy and Pacific Crest Trail Association, objected in a July letter to the Interior Department. They say the administration is fundamentally changing the nature of national parks with little or no public notice or study.

“If you’re hiking on a trail in Utah and you’re rounding a bend and something’s coming at you at 20 mph, that really changes the experience,” said Kristen Brengel, a vice president of the National Parks Conservation Association, a nonprofit that advocates for the national park system.

“It’s pretty jarring” to those who take to public lands to escape city noise and stress for nature, Brengel said. “You’re adding significant speed and a throttle to those trails.”

E-bikes are the fastest-growing segment of the bicycle industry, with U.S. sales jumping 72 percent to $144 million last year, according to the NPD Group, which tracks bike sales. The motorized bikes are popular with commuters and aging baby boomers who might not otherwise get out on a bicycle.