Glacier National Park is trying to get a handle on how many people are using trails along the Going-to-the-Sun Road corridor, but some trail users have questioned the park's methods and the impacts they have on the wilderness experience.

Remote counters using an infrared beam have been installed on park trails to count users, but the devices don't know the difference between a person, a bear, a bird or a mountain goat when a counter is tripped, University of Montana professor Wayne Friemund explained.

In order to properly calibrate the devices and to adjust for wildlife, surveyors also use a digital camera to tell what, exactly, tripped the counter. That raised the ire of Rich Mandl, a longtime National Park Service volunteer and avid hiker.

"I love this park and resent having my privacy invaded in this manner," Mandl wrote in a letter to the Hungry Horse News last week.

But while he regrets the wilderness intrusion, Friemund said the use of cameras boils down to economics - without the cameras, he would have to put a person at the counter to make note of what tripped it, alone and in grizzly bear habitat.

Trail surveyors have done that in the past. Last summer, counters were manned by staff until they were calibrated. This summer, the surveying budget is tighter while the scope is broader, covering most trails along the Sun Road. Friemund noted that a 1988 study used trail counters and cameras.

The trail cameras don't record images that readily identify people, Friemund said. The images are diffused, he said, and the faces and clothing aren't recognizable. In addition, the cameras are used just a few days to calibrate the counters and then are taken down. The counters are left in place for months.

"I appreciate the concern about wilderness values," said Friemund, who is also the director of the UM Wilderness Institute.

Wilderness values aside, numbers coming out of the study to date are startling. The last study, conducted in 1988, recorded about 1,800 people using the Loop Trail in July and August. Last year, the number was 15,000. In 1988, about 26,000 people hiked the Avalanche Creek trail. Last year, the number was closer to 75,000.

But overall park visitation hasn't changed much, Friemund noted. According to park statistics, about 1.817 million people visited Glacier in 1988. The number in 2011 was comparable - 1.853 million. What's happened is the Sun Road shuttle makes it easier to hike certain trails, and people are doing just that - in droves.

Friemund is also surveying park shuttle bus riders. The study will end this year, and the data will be incorporated into the park's Sun Road Corridor Management plan. Work on that plan will start next year and conclude in 2015.

Park managers have already noted that the shuttle service is overloading some trails with more people than the trails were designed to handle.

The shuttle was intended to ease traffic during construction of the Sun Road. While it has done little of that, it has made it easier for visitors to hike loop trails and get to trailheads - two vehicles are no longer needed for some of the longer hikes in the park. The shuttle is also free.

The Highline Trail in summertime sees about 600 hikers a day from Logan Pass, Friemund said. About 250 continue down to The Loop parking area on the Sun Road, and the rest presumably return to Logan Pass.

The trail counter and shuttle bus survey work will wrap up on Labor Day weekend, Friemund said.