Permits were supposed to make climbing Yosemite’s Half Dome safer. They made things worse

An attempt to make Yosemite National Park’s famed 2700-meter-high Half Dome rock formation safer for hikers appears to have backfired.

In 2010, the California park began to issue permits through a random lottery to visitors interested in scaling Half Dome (pictured). It cited overcrowding for its decision; in the decade before, seven people died on the formation, including several who slipped and fell. Media attention focused on the way hikers had to queue and bunch together as they used metal handrails that are drilled into the rock to help people up the final, steepest section. The park hoped the permitting would limit the number of climbers crowded together on the rails at the top, and thus improve safety.

But the permitting appears to have made matters worse, according to a study in press at Wilderness & Environmental Medicine . When researchers analyzed search-and-rescue data on and around Half Dome from 2005 to 2015, they found no significant difference in deaths and injuries after Yosemite began to issue permits. But because the permitting halved the number of visitors who hike the trail, the number of serious incidents per person effectively doubled.

The permits may encourage visitors to take risks, including to keep going if they feel unwell, as they know they might not get another permit—and thus another chance to reach the top, the team speculates. Or the widespread publicity of the permitting process may attract people who are unfit or inexperienced.