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The energy you must expend to complete a trail, path, or route. 

Effort is often estimated by considering some combination of length, total elevation gain, and gradeWe provide more consistent, precise, and potentially more useful estimates by calculating:

As noted elsewhere, a distinguishing feature of our rating system is the distinction between effort (which is easier to objectively rate and more likely to be experienced similarly by all users) and stress which depends on more subjective ratings and more likely to be experienced very differently by different users depending on their mobility challenges).

Some Background

The effort experienced by users on a given path, trail, or route depends primarily on a combination of two factors: the length and either the grades or the total elevation gain. 

  • Grade is the elevation change over a given length - a 10% grade means a 1' elevation change over 10'. Sections with more difficult grades require greater effort to complete. 

  • Total elevation gain commonly 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. More serious cyclists and hikers often use elevation gain to capture the total effort expended going uphill.

Many trail rating systems rely heavily on these dimensions of effort, like the ratings used by the National Parks Service that bases 5 levels of difficulty almost completely on length and elevation gain.    

  • Advantages

    • These dimensions are easier to objectively evaluate. 

    • Effort also varies less across users.  For example, both fit and unfit hikers will find that a longer trail or one with steep grades will require more effort relative to a shorter trail or one with more gentle grades.

  • Disadvantages - existing systems do not work well for those with mobility challenges seeking a local trail.  For example

    • They do not separate out stress and effort

    • They have not been applied to shorter walks

    • They yield very rough estimates - the NPS rating results in 5 levels of difficulty

How we use length, grade and elevation changes to estimate effort

Grade Our goal is to map grades every 10' on paths and trails (and every 30' on routes) whenever running grades exceed Universal Access standards (e.g., are Easy or greater - see below). ​See the example of one part of the Northern Delaware Greenway below. This allows users to easily see where the most difficult grades will be encountered on a walk 

Sample steep descent NDG.png

Thresholds are selected to map onto standards for Universal Access paths, as follows

  • Flat - less than 5%

  • Easy - between 5 and 8.33%

  • Easy to Moderate - between 8.33 and 10%

  • Moderate - between 10 and 12.5%

  • Difficult - between 12.5 and 20%

  • More Difficult - between 20 and 30%

  • Very Difficult - greater than 30%.

Maximum Extra Effort Rating
Maximum Effort 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 Effort Rating of Easy. 

Howe Trail CCW Grade Rating.png
Howe Grades Excel CW.png

You can see to the left that the trail running clockwise has a Maximum Effort 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 Effort 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.

Howe Trail CW new.png

With the map zoomed in, you can see where the Maximum Effort 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. 

Howe Trail CW new detailed.png

For each path, trail, and route we 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. 

Sample Excel table longest continuous grades.png
Longest Continuous Grades
Flat Equivalent Length

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).

  • 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  

  • 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.

  • We combine these calculation in what we call Scarf's correction (see green box to the right) 

Sample Excel table overall grade rating.png

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.

Oversee farmhouse 2.png

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.  

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