Trail Design Calculator

This only happens when ADA Accessible? is on and your original length made for a grade steeper than ADA's 5% max -- in that case, this calculator recomputes the trail's actual buildable length purely from Elevation Gain (ft) at exactly a 5% grade, ignoring the length you typed. Until your entered Trail Length (ft) is long enough on its own to bring the direct-line grade to 5% or under, every length below that produces the identical adjusted length and cost -- the elevation you need to climb, not your guess at distance, is what's governing the trail's real minimum length.

Grade Compliant? is a straight yes/no test of your original Trail Length (ft) and Elevation Gain (ft) against the applicable max grade (5% if ADA Accessible? is on, 10% otherwise) -- it reports 0 whenever the direct-line grade you entered exceeds that limit, even though Adjusted Trail Length (ft) has already worked around it. The two exist together on purpose: Grade Compliant? tells you your ORIGINAL plan doesn't meet the standard, while Adjusted Trail Length (ft) and everything costed from it show what it would take to fix that with switchbacks.

Surface Material (cu yd) is 0 specifically for Boardwalk (Surface Type 4) -- an elevated structure that's priced entirely per square foot ($42.50/sq ft in this calculator's cost table) rather than a bulk-fill depth, so there's no volume figure to report. The other four surface types (crushed stone, asphalt, concrete, natural earth) all compute a real depth-times-area volume, since they're placed as a material layer rather than built as a structure.

No. Average Grade (%) and Grade Compliant? are purely a function of Elevation Gain (ft) divided by Trail Length (ft) -- width has no bearing on slope. Trail Width (ft) instead scales every area- and volume-based quantity (Total Surface Area (sq ft), Aggregate Base (cu yd), Surface Material (cu yd)) and, through them, most of the cost breakdown, but it never enters the grade or switchback-length calculation at all.

Because a design that's already ADA-accessible per this calculator doesn't need them. When ADA Accessible? is on, Adjusted Trail Length (ft) is always sized so the trail's average grade stays at or under 5% (1:20) -- and per the Access Board's Outdoor Developed Areas standard §1017.7 (Trails), no resting interval is required at all when running slope stays at or under that 1:20 threshold. Resting Intervals Needed only becomes nonzero for a non-ADA-accessible trail (ADA Accessible? off) whose average grade exceeds 5%, using Table 1017.7.1's real spacing for that steeper case: one rest area every 200 ft between 5% and 8.33% grade, or every 30 ft between 8.33% and 10%.