WASHINGTON – A Trump administration plan to provide older and disabled citizens greater access to national parks by expanding the use of electric bikes is revving up criticism from nature advocates who say the policy threatens to disturb pristine trails and poses a safety hazard.

The National Park Service (NPS) announced the change Friday, which would allow battery-powered e-bikes that can reach speeds of 28 miles per hour on the same park roads and trails that permit traditional bicycles. The motor may not be used to propel an e-bike without the rider also pedaling, except in locations open to public motor vehicle traffic, under the policy.

“They 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, especially at high altitudes or in hilly or strenuous terrain," said National Park Service Deputy Director P. Daniel Smith.

The change has drawn criticism by park advocates and some trail enthusiasts who say the administration did not do enough to seek public input on a policy that could damage the park experience for many.

“E-bikes have a place on national parks’ roads and motorized trails. But this announcement disregards well-established policies for how visitors can enjoyably and safely experience the backcountry in national parks," said Kristen Brengel, senior vice president at the National Parks Conservation Association. "For generations we’ve agreed that there are some places so special that they should be protected for visitors to enjoy away from the hustle and bustle of everyday life."

Said Tyler Ray, director of policy and advocacy for the American Hiking Society: "Permitting e-bike use on trails that have been thoughtfully and specifically designated as non-motorized raises questions of safety and trail sustainability that must be considered."

An e-bike is classified as a two- or three-wheeled cycle with fully operable pedals and an electric motor of less than 750 watts (1 h.p.) that provides propulsion assistance. Park Service officials note the policy is modeled after a number of states that already allow expanded use of electric bikes.

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In making the announcement, the NPS touted the environmental effects of the new policy, saying the e-bikes can reduce greenhouse gas emissions when used as an alternative to cars and motorcycles and improve poor air quality at national parks by reducing traffic congestion.

Park visitors posting in June (before the policy was announced) on the independent National Parks Traveler web site expressed mixed opinions on the expanded use of the electronic bikes. Some worried the low-humming devices will add congestion, noise and safety risks to normally quiet trails while others said national park trails should be more accessible to those who have physical handicaps.

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"Having an electric bike, I would love the opportunity to enjoy nature trails specific to e bikes," wrote Elizabeth Binnings, who describes herself as a disabled person with limited leg strength. "Obviously not all trails are smooth enough, but it would enhance my enjoyment of life to get out in nature, and isn't that the point of National parks."

"There are plenty of places in most parks for those who are not 'physically able' to enjoy without getting on an e- bike," Alice Tharp posted on the blog. "What's next? Elevators to Angels Landing (at Zion National Park in Utah) for those who can't hike it, a tram ride (at Yosemite National Park in California) to get to the top of El Capitan?