How can a shorter hike be considered more strenuous than much longer hike? This section discusses how hikes gained their accessible, easy, moderate, or strenuous classifications.
For this book I wanted a clear and impartial way to compare hikes. Coming up with a data-driven rating system for hiking trails proved to be very challenging. The existing tools I found were limited. For this first edition of the book I have used the rating system developed by Shenandoah National Park. (Read the full description here.) The Shenandoah National Park uses: √ (Elevation Gain x 2 x Distance) to come up with a rating. For example if a hike is 4 miles long and has 1,000 feet of elevation gain then it is √ (1,000 x 2 x 4.0) = 89. This then gives you a way to compare hikes based on the factors of elevation gain and distance.
This is a great start but it is not complete. As I was creating this book I found that there were many other factors besides distance and elevation gain that had an impact on the difficulty of a hike. Firstly, hikes which begin up high and descend to a lower destination, such as the Western Ute Trail which begins at the Alpine Visitor Center and then leads down to Milner Pass, are shown to be incredibly easy since there is almost no elevation gain along the way. The reality is that a downhill hike, while easier on the lungs, is harder on the knees and feet. It is definitely much harder than the other hikes it is grouped with using this formula.
Secondly, I found that hikes which began at very high elevations such as the very short Alpine Ridge Trail, which also begins at the Alpine Visitor Center, are shown to be far easier than most people experience them. Because you are beginning the hike at nearly 12,000' many people find themselves completely breathless within a minute or two. Some even experience heart attacks or issues of altitude illness on this hike as they start out on what looks like an easy trail. The Shenandoah rating system would put this as one of the easiest hikes in the park, when the reality is that most people who are not well acclimated to the elevation and are not particularly fit will really struggle.
Thirdly, there are many hikes that have one particular segment that should put the hike into a different rating but the Shenandoah formula can't account for it. For example, if you are hiking Estes Cone from either direction, it is a fairly straightforward hike until you reach Storm Pass. At this point the trail becomes very steep with loose rock and a trail that is hard to follow. The formula doesn't take into consideration this section. A hike like Sky Pond is a normal hike until you reach Timberline Falls. At this point you are scrambling with hands and feet up the side of a waterfall. Although the section is short, it really changes the nature of the hike and so there should be some way to account for it.
Lastly, I've found that not all elevation gain is equal. While hiking to The Pool you'll walk up and down many small hills. Most people and children have little trouble with these and many will barely even notice them, but those small hills add up in elevation to 380' of elevation gain on the way there and back. Yet if you were to compare that to 380' of elevation gain all taken in a steady incline it would require much more exertion.
To take all these factors into account, there were a number of hikes in the book that I manually changed their rating so that they better reflected the hiker experience. You’ll find that these hikes have an asterisk next to the difficulty rating. They show my estimated rating and beside it in parenthesis you’ll find the rating provided by the Shenandoah formula. For example, on the Alpine Trail Ridge hike which begins at nearly 12,000’ above sea level, I rated it at 50 but the formula rated it at 16.
So, with all of these limitations I recognize the need for a much better approach to trail rating. I am in discussions with others about different ways to do this. At the moment it looks like the best way will be to start by rating the trails in sections. We're also playing with coming up with some system of determining how much exertion is required for different sections. We're still early in this process but it may eventually make its way into future editions of this book. In the meantime, take these ratings with a grain of salt or focus on reading the descriptions to better compare one trail with another.