Editing Trail (section)

==Construction==
[[Image:Under the rumbling Steinsdalsfossen.png|thumb|alt=Photograph of a trail under a waterfall |A trail constructed under the waterfall [[Steinsdalsfossen]], Norway]]
While most trails have arisen through common usage, the design and construction of good quality new paths is a complex process that requires certain skills.

When a trail passes across a flat area that is not wet, brush, tree limbs and undergrowth are removed to create a clear, walkable trail. A bridge is built when a stream or river is sufficiently deep to make it necessary. Other options are [[culverts]], [[Step-stone bridge|stepping stones]], and shallow fords. For equestrian use, shallow [[Ford (crossing)|fords]] may be preferred. In wet areas an elevated trailway with fill or a [[boardwalk]] is often used, though boardwalks require frequent maintenance and replacement, because boards in poor condition can become slippery and hazardous.<ref>{{Cite web |title=Basic Elements of Trail Design and Trail Layout From "Pathways to Trail Building" |url=https://www.americantrails.org/resources/basic-elements-of-trail-design-and-trail-layout |url-status=live |access-date=7 February 2021 |website=americantrails.org |archive-date=28 October 2020 |archive-url=https://web.archive.org/web/20201028002313/https://www.americantrails.org/resources/basic-elements-of-trail-design-and-trail-layout }}</ref>

===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.

===Drainage===
{{More citations needed section|date=February 2021}}
[[Image:Waterbar.jpg|left|thumb|upright|alt=Photograph showing a waterbar drainage ditch to the left, the trail to the right |A [[waterbar]] in New York's [[Catskill Mountains]]. The trail forks right; the drainage ditch is to the left.]]
Trail construction requires proper drainage. If drainage is inadequate, three issues may occur: water may accumulate on flat terrain to the point that the trail becomes unusable; moving water can erode trails on slopes; or inadequate drainage may create local mud spots. Mountain bike trails slope out or across the trail 3–5% downhill to encourage water to run off the side, rather than down the trail bed.<ref name=DBST>{{Cite web |title=Designing and Building Sustainable Trails |url=https://imbacanada.com/designing-and-building-sustainable-trails/ |url-status=live |access-date=7 February 2021 |website=imbaccanada.com |archive-date=14 January 2021 |archive-url=https://web.archive.org/web/20210114114705/https://imbacanada.com/designing-and-building-sustainable-trails/ }}</ref>

To remedy the first problem, water accumulation on flat terrain, raised walkways are often built. They include turnpikes, causeways, embankments, stepping stones, and bridges (or deckwalks).<ref>{{Cite web |url=http://www.sctrails.net/trails/LIBRARY/TrailTerms.htm |title=Glossary of Trail and Greenway Terms |date=2008 |publisher=South Carolina State Trails Program |url-status=dead |archive-url=https://web.archive.org/web/20140413061637/http://www.sctrails.net/trails/library/trailterms.htm |archive-date=13 April 2014 |access-date=5 January 2014}}</ref> The earthen approaches are often done by cutting poles from the woods, staking parallel poles in place on the ground, then filling between them with whatever material is available to create the raised walkway. The more elaborate option of the deckwalk is by necessity reserved for shorter stretches in very high-traffic areas. Water accumulation is particularly common in the [[Northern England|North Country]] of England.

The second problem, water erosion, is caused because trails, by their nature, tend to become [[drainage]] channels and eventually gullies when the drainage is poorly controlled. Where a trail is near the top of a hill or ridge, this is usually a minor issue, but when it is farther down, it can become a very major one.

In areas of heavy water flow along a trail, a ditch is often dug on the uphill side of the trail with drainage points across the trail. The cross-drainage is also accomplished by means of culverts cleared on a semi-annual basis, or by means of cross-channels, often created by placing logs or timbers across the trail in a downhill direction, called "thank-you-marms", "deadmen", or '''[[waterbars]]'''. Timbers or rocks are also used for this purpose to create erosion barriers. Rock paving in the bottom of these channels and in the trailside ditches is sometimes used to maintain stability. The creation of water bars, with or without ditching, at major points of water flow on or along the trail, and in conjunction with existing drainage channels below the trail, is a technique that can be applied. Another technique that has been adopted is the construction of '''coweeta dips''', or drain dips, points on the trail where it falls briefly (for a meter or so) and then rises again. These provide positive drainage points that are almost never clogged by debris.
[[File:Black Hill (Peak District).jpg|thumb|alt= Photograph of a stone path laid across boggy ground |[[Black Hill (Peak District)]], Cheshire, England, where a stone path was laid across boggy ground]]
The third type of problem can occur both on bottomlands and on ridgetops and a variety of other spots. A local spot or short stretch of the trail may be chronically wet. If the trail is not directly on rock, then a mud pit forms.  Trail users go to the side of the trail to avoid the mud pit, and the trail becomes widened. A "corduroy" is a technique used when an area cannot be drained. This ranges from random sticks to split logs being laid across the path. Some early turnpikes in the United States were [[corduroy road]]s, and these can still be found in third-world forested areas. With recreational trails, it is common for the sticks to be one to three inches thick and laid in place, close together. Sometimes, a short bridge is used.<ref name=DBST/>

===Maintenance===
Natural surface, single-track trails will require some ongoing maintenance. If the trail is properly designed and constructed, maintenance should be limited to clearing downed trees, trimming back brush and clearing drainages. Depending on location, if the trail is properly designed, there should be no need for major rework such as grading or erosion control efforts. Mountain trails which see both significant rainfall and human traffic may require "trail hardening" efforts to prevent further erosion. Most of the seemingly natural rock steps on the mountain trails of the northeast United States are the work of professional and volunteer trail crews.<ref name=DBST/>

===Navigation===<!-- This section is linked from [[Tuscarora Trail]] -->
{{Main|Trail blazing}}
[[Image:Trail blaze-symbols.svg|left|thumb|alt=Illustration of the common symbols used in trail blazing in the US |The most common symbols used in [[trail blazing]] in the US]]

For long-distance trails, or trails where there is any possibility of someone taking a wrong turn, '''[[Trail blazing|blazing]]''' or signage is provided (the term [[waymarking]] is used in Britain). This is accomplished by using either paint on natural surfaces or by placing pre-made medallions or sometimes [[cairn]]s. Horseshoe-shaped blazes are used frequently for bridle trails. The [[Appalachian Trail]] is blazed with white rectangles, and blue is often used for side trails. [[European long-distance path|European long-distance walking paths]] are blazed with yellow points encircled with red. Other walking paths in European countries are blazed in a variety of manners.

Where bike trails intersect with pedestrian or equestrian trails, signage at the intersections and high visibility onto the intersecting trails are needed to prevent collisions between fast-moving cyclists and slower moving hikers and horses. Bicycles and horses can share the same trails where the trail is wide enough with good visibility.  The US Department of Transportation provides standards and guidelines for traffic control, including signage and striping, for bicycle facilities.<ref>{{Cite book |title=The Manual on Uniformed Traffic Control Devices (MUTCD) |year=2009 |chapter=9 |chapter-url=https://mutcd.fhwa.dot.gov/ |access-date=19 December 2011 |archive-date=11 November 2019 |archive-url=https://web.archive.org/web/20191111063902/https://mutcd.fhwa.dot.gov/ |url-status=live }}</ref>

=== Classification ===
[[File:BergAlpinWegweiser.jpg|thumb|Swiss signs: hiking trails in yellow,<br />mountain path in white-red-white,<br />Alpine Route in white-blue-white]]

A simple colored symbol to classify a trail's difficulty in the USA was first used for ski trails and is now being used for hiking, bicycle, other trails.<ref>{{Cite web |url=http://www.skinet.com/ski/transportation-security-administration/2008/11/signs-of-the-times |title=Signs of the Times |last=John Fry |date=November 2008 |publisher=SKI Magazine |access-date=25 August 2011 |archive-url=https://web.archive.org/web/20160323105049/http://www.skinet.com/ski/transportation-security-administration/2008/11/signs-of-the-times |archive-date=23 March 2016 |url-status=usurped }}</ref><ref>{{Cite web |url=http://www.fs.usda.gov/wps/portal/fsinternet/!ut/p/c5/04_SB8K8xLLM9MSSzPy8xBz9CP0os3gDfxMDT8MwRydLA1cj72BTSw8jAwgAykeaxcN4jhYG_h4eYX5hPgYwefy6w0H24dcPNgEHcDTQ9_PIz03VL8iNMMgycVQEAIzTHkw!/dl3/d3/L2dJQSEvUUt3QS9ZQnZ3LzZfMjAwMDAwMDBBODBPSEhWTjJNMDAwMDAwMDA!/?navtype=&cid=stelprdb5103006&navid=110160000000000&pnavid=110000000000000&ss=110618&position=Not%20Yet%20Determined.Html&ttype=detail&pname=Willamette%20National%20Forest-%20Hiking |title=Trails/Hiking: Explanation of Trail Difficulty |publisher=US Forest Service |access-date=25 August 2011 |archive-date=7 November 2012 |archive-url=https://web.archive.org/web/20121107204736/http://www.fs.usda.gov/wps/portal/fsinternet/!ut/p/c5/04_SB8K8xLLM9MSSzPy8xBz9CP0os3gDfxMDT8MwRydLA1cj72BTSw8jAwgAykeaxcN4jhYG_h4eYX5hPgYwefy6w0H24dcPNgEHcDTQ9_PIz03VL8iNMMgycVQEAIzTHkw!/dl3/d3/L2dJQSEvUUt3QS9ZQnZ3LzZfMjAwMDAwMDBBODBPSEhWTjJNMDAwMDAwMDA!/?navtype=&cid=stelprdb5103006&navid=110160000000000&pnavid=110000000000000&ss=110618&position=Not%20Yet%20Determined.Html&ttype=detail&pname=Willamette%20National%20Forest-%20Hiking |url-status=live }}</ref>
*Green circle – easy
*Blue square – moderate
*Black diamond – difficult

Other systems may be used in different locations.<ref>[http://www.trentu.ca/academic/trailstudies/difficult.html Trail Difficulty Classification] {{Webarchive|url=https://web.archive.org/web/20170216193602/http://www.trentu.ca/academic/trailstudies/difficult.html |date=16 February 2017 }}. Trail Studies Unit, [[Trent University]]. Retrieved 25 August 2009.</ref><ref>[http://everything2.com/title/Ski+trail+difficulty+classifications Ski trail difficulty classifications] {{Webarchive|url=https://web.archive.org/web/20170802112959/https://everything2.com/title/Ski+trail+difficulty+classifications |date=2 August 2017 }}. gavmck, [[Everything2]], 4 June 2004. Retrieved 25 August 2009.</ref>

In Switzerland, paths are classified by three levels of difficulties: Hiking paths (yellow markers), mountain paths (white-red-white markers) and alpine paths (white-blue-white markers).