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Trail Effort
The energy you must expend to complete a trail, path, or route.
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Trail Effort is the fitness level needed to complete a walk. It is primarily determined by the
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Length of the walk, and
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Combined Running Grade which generally considers both the Length AND Grade of uphill sections
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​Grade: the elevation change over a given length - a 10% grade means a 1' elevation change over 10' of travel.
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Running Grade is in the direction of travel
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Cross-Grade is perpendicular to it
Relationships between Length, Grade, and Effort are likely the same for those with and without disabilities.
People with disabilities can reach goals to increase fitness by choosing trails that are longer and/or have more challenging grades.
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General Grade Rating
Grade Levels: Levels 1-4 are selected to be able to map directly onto Universal Access (UA) Standards
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Flat - less than 5%
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Easy - between 5 and 8.33%
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Easy to Moderate - between 8.33 and 10%
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Moderate - between 10 and 12.5%
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Difficult - between 12.5 and 20%
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Very Difficult - between 20 and 30%
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Extremely Difficult - greater than 30%.
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Our Running Grades are drawn from UA Standards described below, which consider the length and grade of uphill sections
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A+ Running Grade
These are consistent with federal standards for Shared Use Paths (Trails for All People, p. 68), and are met by most Multi-Use Paths and some Natural Trails
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No section has running grades greater than 5%
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Example: The Chester Valley Trail, pictured right
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A Running Grades
These are consistent with Standards for UA Paths (Trails for All People, p. 30). .These include a mix of sections varying in grade and length as follows
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Easy (5-8.33%): No sections more than 200' long
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Easy to Moderate (8.33-10%): No sections more than 60' long
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Moderate (10-12.5%): No sections more than 10' long
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No sections with grades greater that 12.5%
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This combination is intended to include grades presumed to not exceed the fitness and stress-tolerance of people with disabilities. For example a wheelchair user may
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Finder longer uphill sections with easy grades to challenge their fitness
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Shorter sections with steeper uphill OR downhill grades create stress
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A- Running Grades
A few Multi-Use Paths and some Natural Trails have the longer and/or steeper sections below that exceed UA standards but could still be accessible depending on users' fitness​
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Easy (Up to 8.33%): Any length
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Easy to Moderate (8.33-10%): No sections more than 200' long
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Moderate (10-12.5%): No sections more than 60' long
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Difficult (12.5-20%): No sections more than 10' long
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No sections with greater than 20% Grades
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Example: The East Branch Brandywine Trail Pictured right) has a 50' long section at the southern end with 11% grades ​
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B Running Grades
Many unimproved Natural Trails in wilderness areas might include these grades
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Easy to Moderate (Up to 10%): Any length
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Moderate (10-12.5%): No sections more than 200' long
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Difficult (12.5-20%): No sections more than 60' long
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More Difficult (20-30%): No sections more than 10' long
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No sections have grades greater than 30%
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Example: The western half of the Northern Delaware Greenway is one of very few Multi-Use in the region to be rated B because of Difficult sections more than 60' long (e.g., to climb up the cliffs from the Brandywine pictured here).
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Only more fit and experienced users with disabilities would be comfortable on these trails.
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C Running Grades
Many Natural Trails in more rugged and hilly areas would meet these criteria
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Moderate (Up to 12.5%): Any length
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Difficult (12.5-20%): No sections more than 200' long
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More Difficult (20-30%): No sections more than 60' long
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Very Difficult (Greater than 30%): No sections more than 10' long
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Other Considerations
Resting intervals
In the federal standards for Universal Access Trails (Trails for All People, p. 32), these 5' wide and 5' long flat sections reset sections with Running Grades that exceed 5%. For example, a path with a 390' section with Easy to Moderate grades would merit an A- Running Grade Rating . The same path with a Resting Space that broke up the 400' section above into 2 sections less than 200' long would merit an A Running Grade Rating
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Why is this important? Resting intervals give wheelchair users a chance to catch their breath on sections that approach the maximum length/running grade combinations listed above.
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​Easy Grades still require effort!
Work can still be required on a path with Running Grades rated as A+! This beautiful 600' boardwalk section of the Jack Markell Trail complies with standards for shared use paths because it never exceeds a 5% grade. Nonetheless, its length would make it difficult - and potentially stressful - for users with disabilities who are less experienced or less fit.
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Capturing Grades & Effort
We have explored easy ways to map grades every 10' on paths and trails consistent with the system described above. Here is an example from the Northern Delaware Greenway with the steepest sections (heading west). This allows users to easily see where the most difficult grades will be encountered on a walk.​
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We have sought to use elevation changes derived from trails overlayed onto online Digital Elevation Maps
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The challenge? Online maps vary in their precision: while they might capture overall elevation changes, they might not be accurate enough to capture places where a "cut" was made for a route to moderate a steep section
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An option? Conduct site visits to verify specific sections
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We have developed spreadsheets that summarize grade data and automatically calculate the elevation changes in each needed to assign Combined Running Grade Ratings. ​
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In this example, A+ is Unshaded, A is shaded Green, A- is shaded Yellow, and B is shaded Light Pink.
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This suggests that a B rating may just be merited, because of 30' sections of Difficult Uphill Grades (See red arrow)
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Other possible ways to capture effort
The total elevation gain is one of the most common ways of calculating effort. This refers to the sum of elevation gain across an entire trip (see Wikipedia). For example, you might descend 20 feet, then go 20 feet up a hill, descend 20 feet, and finally go 20 feet up another hill. This represents a total elevation gain of 40 feet, even though your altitude is unchanged. But this does not distinguish between sections with easier versus more difficult grades: for some, a 10' section of difficult grades may be a barrier.
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​​We might also consider trying to estimate Effort by considering other combinations of length, total elevation gain, and grade. We provide more consistent, precise, and potentially more useful estimates by calculating:
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The Maximum Grade Rating. This captures when grades become increasingly difficult.
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The Flat Equivalent Length. This might helps compare trails of different lengths but with different grades.
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The Longest Continuous Grades. These are the sections requiring the most effort.
- We also recognized the benefits of mapping grades for each direction separately, because grades may be longer but gentler in one direction, which some walkers might find more comfortable.
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Maximum Grade Rating
​We base this on the same combination of grades referenced in federal law related to Universal Access Walking (Pedestrian Only) Trails summarized by Knutson and his colleagues in their 2021 guide. It is expressed as a combination of grade and length as seen in the table to the right created for the Howe Trail (running counter clockwise). The existence of one 10' section with Moderate Uphill Grades and 2 200' sections with Easy Uphill Grades shifts this trail into a Maximum GradeRating of Easy.
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You can see to the left that the trail running clockwise has a Maximum Grade Rating of Hard because of 2 30' sections of Difficult Uphill grades. So though while this trail loop necessarily has the same total elevation gain in both directions, the presences of steeper uphill sections may make one direction easy for some users.
We have also begin to note when the point at which a longer or steeper section shifts the Maximum Grade Rating upwards. This allows users to decide whether a portion of the trail is worth completing, if the overall trail includes sections that are just too difficult. We mark the transitions to more difficult grades on the map so that users can see when these sections start. In the example below corresponding to the trail described above heading clockwise, you can see the green marker 1 followed quickly by the yellow marker 2 and the red Marker 3.
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With the map zoomed in, you can see where the Maximum Grade Rating shifts because of upcoming uphill grades. The shift from UA to Easy occurs where the average uphill grade for the next 200' became Easy (5-8.33%). It then shifts from Easy to Hard and then to Hard because of average uphill 30' overlapping sections requiring Moderate (10-12.5%) and Difficult Effort (12.5-20%) respectively.
For each path, trail, and route we might also list the longest continuous uphill and downhill grades (outlined in red to the right). This helps certain users (like wheelchair users) who may find long uphill AND downhill grades for challenging. In the example below, the longest continuous grades are marked with the red rectangle in the spreadsheet used to generate our ratings.
CASE STUDY This 1.3 mile loop has a Flat Equivalent Length of 1.5 miles and merits an Overall Grade Rating of Easy. Depending on the direction, the longest continuous grades are as follows: a 260-530' section with at least easy grades, a 80-100' section with at least easy to moderate grades, a 80-100' section with at least moderate grades, and a 20-50' section with at least difficult grades.
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Flat equivalent length
How do you compare the overall effort required for two trails that differ in length and total elevation gain? We generate an estimate of the flat equivalent length, or the distance one might cover completing this path, trail, or route if it were flat (we do not generate this for Universal Access trails, because the difference is negligible).​
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Scarf’s equivalence, (based on Naismith’s rule) to claims that every foot of positive elevation change is equivalent to walking about 8 feet. For example, walking a 10' section with a 12.5% grade is equivalent to walking 20' on a flat section. We apply this formula to positive elevation change
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Since walking downhill takes less effort, we propose that one foot of negative elevation change decreases effort by 10%. So walking a 10' section with a 10% downhill grade is like walking 9' on a flat section.
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We combine these calculation in what we call Scarf's correction (see green box to the right)
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Knowing the speed that you can comfortably walk, and the length of time you can comfortably walk on a flat trail, you can predict how comfortable you will be on a new trail.
CASE STUDY Margot's favorite walk is the 1.2 mile long Oversee Farm Trail, which she walks most Saturday mornings as long as the weather is good. About 20% involves uphill grades ranging from easy to difficult, and resulting in a Flat Equivalent Length of 1.4 miles. Margot walks this comfortably in 75 minutes (with a break). So she should be able to comfortably walk other trails with the same flat equivalent length in about the same amount of time.