OLYMPIC NATIONAL FOREST (AP) — Tucked amid moss and decaying branches in Olympic National Forest, infrared trail counters are helping forest managers better understand when and where people hike.

The U.S. Forest Service is experimenting with the pupil-sized lens that uses infrared scopes to register the heat signature from warm, moving objects.

The data gathered will help the agency better manage human impacts on wilderness areas, as well as know where and when to deploy staff.

“We always had to guess at the numbers,” Olympic’s wilderness manager Alex Weinberg said. “Now we have a concrete way of telling how much use we’re getting.”

Starting in late August, Weinberg installed counters on five trails on Olympic’s west side, including Upper Big Quilcene, the Lower Mount Ellinor, Upper Mount Ellinor, Mount Townsend and Tubal Cain.