Yosemite National Park uses a trailhead quota system to manage wilderness visitors. Park scientists set user capacities in the 1970s for wilderness zones and trailhead quotas from prevalent travel patterns and a computer simulation model. Limiting how many visitors start daily at a trailhead maintains overnight zone use within capacity if trip characteristics (party size, trip duration, spatiotemporal itinerary adherence) remain similar to the 1970s. Evidence suggests that travel patterns have changed since this system's inception. Data on which the original trailhead quotas were based, and the data on itinerary adherence, are nearly forty years old, and the supposition is that visitor use consists of a larger number of shorter distance and shorter duration trips. Consequently, travel zone capacities are likely being exceeded in some zones on high-use nights. To accurately assess wilderness use distribution and to develop a contemporary travel simulation model, wilderness trips from 1 May - 30 September 2010 were evaluated in regard to mean party size, trip duration, and spatial and temporal adherence to the permit itinerary. Multiple visitor use scenarios (e.g. alternate trailhead permit quotas) were then simulated and the results presented to Yosemite Wilderness managers.

Mark subsequently earned his Ph.D. at the University of Montana in Missoula and is currently an assistant professor at the University of Maine at Machias