Editing Trail (section)

===Slopes===
{{More citations needed section|date=February 2021}}
Trail gradients are determined based on a site specific assessment of soils and geology, drainage patterns of the slope, surrounding vegetation types, position on the slope of a given trail segment (bottom, mid-slope, ridgeline), average precipitation, storm intensities, types of use, volume and intensity of use, and a host of other factors affecting the ability of the trail substrate to resist erosion and provide a navigable surface. Trails that ascend steep slopes may use [[hairpin turn|switchback]]s, but switchback design and construction is a specialized topic.

Trails that are accessible by users with disabilities are mandated by the U.S. Federal Government to have slope of less than 12%, with no more than 30% of the trail having slope greater than 8.33%.<ref>{{cite web|url=https://www.access-board.gov/files/aba/guides/outdoor-guide.pdf|pages=24–25|publisher=United States Access Board|year=2014|title=Accessibility standards for Federal outdoor developed areas}}</ref>

Trails outside of wilderness areas have outward side-to-side gradients less than 8%,.<ref name=NCT>{{cite web|url=https://www.nps.gov/noco/learn/management/upload/NCT_CH4.pdf|title=Standards for Trail Construction|work=Handbook for Trail Design and Construction and Maintenance|publisher=National Park Service|year=1998}}</ref> A flat or inward-sloping trail collects water and causes extra trail maintenance.<ref name=NCT/> The ideal path is built almost, but not quite, level in cross-section.

To achieve a proper slope in hilly terrain, a '''sidehill''' trail is excavated. This type of trailway is created by establishing a line of a suitable slope across a hillside, which is then dug out by means of a [[mattock]] or similar tool. This may be a '''full-bench''' trail, where the treadway is only on the firm ground surface after the overlying soil is removed and sidecast (thrown to the side as waste), or a '''half-bench''' trail, where soil is removed and packed to the side so that the treadway is half on firm old ground and half on new packed fill. In areas near drainages, creeks and other waterways, excavation spoils are taken away in bulk and deposited in an environmentally benign area. Trails are established entirely on fill in problem areas. In such cases, the soil is packed down firmly and the site is periodically checked to maintain the stability of the trail.
[[Image:Mohonk Mountain House 2011 Hiking Trail against Guest Rooms 2 FRD 3281.jpg|thumb|alt=A stairway trail on the side of a hill overlooking a river |Parts of many hiking trails at [[Mohonk Mountain House]] include stairway trails]]

Cycle trails built for commuting may be built to a different set of standards than pedestrian-only trails and, in some cases, may require a harder surface, fewer changes in grade and slope, increased sight visibility, and fewer sharp changes in direction. On the other hand, the cross-slope of a bicycle trail may be significantly greater than a foot trail, and the path may be narrower in some cases. The [[American Association of State Highway and Transportation Officials]] recommends different widths for different types of bicycle facilities.<ref name="aashto">{{Cite web |url=https://safety.fhwa.dot.gov/ped_bike/docs/b_aashtobik.pdf |title=Guide for the development of bicycle facilities |year=1999 |publisher=American Association of State Highway and Transportation Officials |access-date=20 December 2011 |archive-date=15 October 2011 |archive-url=https://web.archive.org/web/20111015204727/http://safety.fhwa.dot.gov/ped_bike/docs/b_aashtobik.pdf |url-status=live }}</ref> For example, a shared use path has a recommended one directional width of {{convert|8|ft|m|2}}, while a bidirectional path should be significantly wider ({{convert|10|to|12|ft|m|2|disp=or}}) to accommodate bidirectional traffic and users.  The US Department of Transportation provides additional guidance on recreational bicycle and pedestrian trail planning and design standards.<ref>{{Cite web |url=http://www.fhwa.dot.gov/environment/rectrails/manuals.htm |title=Manuals and Guides for Trail Design, Construction, Maintenance, and Operation, and for Signs |publisher=US Federal Highway Administration |website=[[Federal Highway Administration|Federal Highway Administration (FHWA)]] |access-date=19 December 2011 |archive-date=18 December 2011 |archive-url=https://web.archive.org/web/20111218125937/http://www.fhwa.dot.gov/environment/rectrails/manuals.htm |url-status=dead }}</ref>

A well designed recreational [[mountain bike]] path for the exclusive use of bicycles has an average grade of less than 10% and generally follows a [[contour line]], rather than straight downhill.