Appalachian Trail Visitation Study Has Breakthrough Implications for Linear Park Visitor Tallies

Hikers on the Appalachian Trail. NPS photo.

Survey research experts are developing new procedures for obtaining Appalachian Trail visitation estimates. If the new sampling procedures and related analytical techniques pan out, we’ll be able to obtain much more defensible visitation tallies for linear parks with numerous unmonitored access points.

Nobody has much confidence in the annual visitation figures cited for the 2,178 mile-long Appalachian National Scenic Trail. The National Park Service, which doesn’t get visitation reports from this particular National Park System unit, thinks it might be around four million, but that’s just a guesstimate. Various other guesstimates place it higher or lower, and none lay claim to accuracy.

Obviously, planners and managers would like to have more defensible numbers to work with. Unfortunately, there are serious flaws in the procedures currently used to obtain visitation estimates for the AT and other trails or linear parks traversing lengthy stretches of backcountry with numerous unmonitored access points.

Enter the AT- and U.S. Forest Service-sponsored Appalachian National Scenic Trail Pilot Survey, the abstract of which reads as follows:

…. This research develops a stratified random survey design which utilizes two survey
instruments, exit site tallies, and a survey questionnaire to obtain visitation estimates on a portion of the AT. The design identifies three components (nonproxy, proxy, and Special Days) which can be used to subdivide the sampling frame into estimator types that lead to more efficient sampling and estimation processes. In addition, design-based and model-assisted approaches are used to obtain estimates for comparison purposes.

The survey was performed from June 1 through August 14, 2007, on a 109-mile stretch of the AT from Harpers Ferry, WV, to ten trail miles north of Boiling Springs, PA at the Scott Farm. Visitation estimates were 66,967 for the design-based approach and 70,912 for the model assisted approach, with coefficients of variation of 23% and 16%, respectively. Individual strata level visitation estimates were quite variable and differed substantially between the two approaches.

An extrapolation to the entire trail for the whole year was performed by developing an
appropriate sampling frame from which the strata weights could be obtained. Based on the
model-assisted approach and assuming the Survey data were representative, the 2007 annual
visitation extrapolation for the entire trail was 1,948,701 with a coefficient of variation of 20%. [Italics added for emphasis]

If this intrigues you, consider reading the entire document. It’s technical, though, and runs to 127 pages, including cited literature and appendices.

The fact that this pilot study placed the AT’s annual visitation at around two million – about half the size of the figure currently cited on the homepage of the Park Service’s AT website -- underscores the scale and complexity of the problem at hand. There is much work to be done before officials will be able to believe in the numbers they are reporting and using to support planning and policy- and decision-making.

The work right now is centered on testing and refining the survey design so it can be counted on (no pun intended) to deliver a tally of AT hikers that is as scientifically rigorous as we know how to make it. As the Park Service put it in a recent press release, “We have a long way to go, but we now have a solid process in place to move forward ….”

Though best-suited to tallying hikers on lengthy backcountry trails, the new methodology should also be suitable for use, with appropriate modifications, in river corridors and other linear-shaped components of the National Park System.