Optimizing trail grade: the key to creating sought-after trails
Designers and land managers should consider the benefits of lengthening trails to lower the average grade while at the same time including short sections that are much steeper.
By Randy Martin
Designing trails that maximize the user’s delight while minimizing the drudgery may be the trail building community’s best way to help energize local economies. It may be a small contribution, but recovery is a process of people becoming confident and deciding to move forward, this could be our part.
Delight vs. Drudgery
Too often, trails are designed in a manner that causes the user to experience unnecessary drudgery with too little delight, thus discouraging repeated use of the trail. Tourists do not travel to Disneyland to ride the parking tram, they go for the Matterhorn. In many areas, tourism is the life-blood of the community, so if the goal is to increase tourism by creating trails, we must keep in mind that a person considering whether or not to travel and use a trail is forgoing a long list of other interesting options. As trail builders and designers we must seek to make our trails attractive.
The purpose of this article is to encourage designers and land managers to consider the benefits of lengthening trails to lower the Average Grade while at the same time encouraging the building of short sections with a Specific Grade (5-10 feet of vertical) to be as steep as the condition will allow. For the sake of simplicity, let’s call this Minimize/Maximize Design.
The key to an enjoyable average tread grade is to keep it as low as reasonable while fulfilling the objectives of the trail. It may be that an objective is to get to the summit, a pass, or to a vista. Most designers I have worked with tend to set the grade at 10% and grind it out. Minimize/Maximize Design lowers the average grade to 4-6% and doubles the length of the trail in a series of grade adjustments.
The optimal average grade will allow higher speed going uphill and releasing earned elevation slowly rewards the user with a nice, long downhill. It is discouraging to spend 40 minutes grinding up a hill only to use it all up in 2-3 minutes. As a friend of mine says, “You want to consume that ice cream cone one lick at a time.”
Although it takes some energy to place one foot in front of the other or roll on the flats, the key heart demand is based on how much elevation is being gained or lost. Depending upon what shape we are in will determine how many feet of elevation per minute can be accomplished. I like to think of elevation in terms of flights of stairs per minute. Let’s say a runner is in pretty good shape and can run eight miles per hour while gaining 10 feet of elevation each minute, (one flight of stairs). That same runner would slow to about 1-2 miles per hour if the sustained grade is 16% (eight flights of stairs per minute). The climbing rates for a bicyclist are similar. Who wants to ride a bike or run under 2 miles per hour? Not me!
The downhill direction is a different experience. The designed grade dictates if the experience is a delightful payoff for the work done to get to the top or just a leg pounding, brake burning, trail grinding experience. If the tread grade is 10% or more, a cyclist will often be on the brakes, which is not much fun and can be hard on the trail. The runner will be in small step braking mode, as are horses and hikers. At a 4% grade, the cyclist can pedal downhill or coast without much braking and a runner can flow effortless down the hill with minimum pounding. As a runner, it is pure delight to be able to run fast downhill without the associated pounding from braking with every step.
There is much discussion of maximum average grade in terms of its sustainability. Rarely have I seen discussion about specific grade. In other words, how steep can a trail tread be for 20 to 40 feet and still be resistant to erosion? Consideration for erosion include soil conditions, typical rainfall, characteristics of the rain delivery, tree canopy, wind, and level of trail use. To maximize the delight of the trail, the specific grade should vary as widely as reasonable. The table to the right is an example of a trail with an average grade of 4%, yet in a 700 foot ascent the grade varied from -5% to 20% and changed 10 times. This is one way to make a trail interesting..
What is called the half rule applies to specific grade: The slope of the trail should not be more than one half the cross slope. This has the most application in less steep areas. The reason for this rule is if the trail is too steep, relative to the slope of the hill, water will tend to collect and run down the trail instead of sheet flowing across the trail and down the hill. Keep in mind that every turn violates this rule at one point. Grade reversals (dips), if used generously, force the water off the trail and can counter violations of this rule.
Foresthill Divide and Connector, Auburn CA
In Auburn California we have a trail where the average grade from top to bottom over 7 miles is only 1.4% while the specific grade ranges from -20% to +22%. It is famous in the region. The lack of a need to summit freed this design to promote plenty of undulating fun in both directions.
Susanville Ranch Park Expansion
Last fall, Trailscape inc. contracted for the finish flagging and construction of 14 miles of trail in Susanville, California. The terrain dictated over 1000 feet of climbing and we were able to stretch the climb to just over 4 miles and we averaged 4.5% grade. As you see below, the climb is fairly steady but is made up of a series of undulations which create delight while climbing and a roller coaster on the way down.
User groups Minimum/Maximum design does not serve well
Physically Challenged: if a 30’ undulation is up to 20% tread grade the accessibility of the trail is minimized. To serve this group while maintaining the excitement, I would keep the maximum tread grade down to 8% on short sections for the first mile from the parking area.
Robust Hikers: One of the challenges for a hiker is that they can only walk so fast before it becomes a run. Often retired, runners turn to hiking as they get older and they rely on a steep trail to get their heart rate up. The short sections of intensity may not satisfy them. To help serve this group, one leg of the loop could be a gradual climb to the summit and one leg of the loop could be made steeper for more advanced hikers.
Extreme Equestrian and Mountain Biking: For the more adventuresome Minimum/Maximum design will not generate the adrenaline desired by the more extreme enthusiasts but it will serve them better than a consistent grade. To help satisfy this group, more difficult optional trail segments may be built in to satisfy some this need.
User groups this trail design serves:
In every group except hikers greater physical demand can be attained by going slightly faster.
We used these concepts when designing the Susanville Ranch Park Trails. These are some comments we have received: "After riding some of the new trail network, I am renewed and excited about cycling again!... I found myself at the truck after a ride yesterday giddy with anticipation of my next ride up there…. I can’t believe I moved away a year before this trail was built. I want to move back." —Stu Speer
"I am truly at a loss for words to describe what you have done for our community and for the mountain bikers, hikers, etc. What an incredible job. Thank you so much. …The sustained climb gives you a great feeling of accomplishment as well. It is rewarding to climb all of the switchbacks and make it to the top without putting a foot down. When I get out there like that I can play with 50 year old people or 10 year old kids and we all feel the same age, wonderful isn't it." —Mike Morgan
I invite you to begin noticing which trails in your area are the favorites and which ones are used less. You may discover that the key to a trail worth traveling for is a low average grade with plenty of variation in specific grades.
Randy Martin is president of Trailscape inc. and can be reached through his website Trailscape.net or Randy@trailscape.net. Footage taken at the Susanville Ranch Park can be seen at youtube.com/trailscape
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Updated February 1, 2009