Science Fair Project Encyclopedia
A trail, in the most general sense, is any linear route for travel. Even highways are sometimes called trails. However, in common usage, a trail is an unpaved, narrow pathway, usually through a wild area, for use by hikers, horseback riders, bicyclists, motorcyclists, or other sport users (Trail Riding). Many trails are off-limits to everyone other than hikers, and few trails allow motorized vehicles.
Trail types and use
Trail use has become very popular for a wide variety of users. Some trails are designated as nature trails, and are used by people learning about the natural world. Many trails are designated day trails, meaning that they are generally used by people out for a short hike, less than a day. Some trails are designated backpacking trails, or long-distance trails, and are used by both day hikers and by backpackers. Some of the trails are over a thousand miles long and may be hiked in sections by backpackers, or completed in one trip by dedicated hikers. Some trails are specifically used by other outdoor enthusiasts to gain access to another feature, such as good climbing sites. Many runners also favor running on trails rather than pavement, as giving a more vigorous workout and better developing agility skills, as well as providing a more pleasant exercise environment.
Vehicular and equestrian trails
Recent decades have seen an explosion of interest in bicycling, both street-type and off-road type. Many graded, surfaced bike paths have been built, but especially popular is the off-road, or mountain biking. These trails must be built to a different set of standards than foot trails, requiring more stable, harder surfaces, less strenuous slopes, and less sharp changes in direction. A particular offshoot of trail biking is downhilling, which can be extremely environmentally destructive if not well-managed.
Horseback riding has continued to be a popular activity for many trail users. Again, horse trails must be built to different standards than other trails.
Motorized trail use also remains very popular with some people. Such terms as ORV, four-wheeling, all-terrain vehicle, and others actually have highly specific meanings. In the United States, this group of people have a very strong political lobby. The Recreational Trail Program defined as part of the Intermodal Surface Transportation Efficiency Act (ISTEA, pronounced "ice tea") of 1991 mandates that seventy percent of its funding be used for motorized trails, with the remaining thirty percent used for dedicated foot trails.
Urban and suburban trails
Though the term "trail" conjures up images of a well-beaten path in a woodland setting, more and more frequently, the term is coming to refer to any sort transportation route designed for non-automobile traffic. For example, a trend sweeping America, especially in the rural Northeast is the conversion of abandoned railways into rail trails . Examples include the Ashuwillticook Rail Trail in Berkshire County and the Northern RailTrail of New Hampshire. Though these wide, often paved pathways could have easily been used as roads, their focus on recreational use for pedestrians and cyclists is what sets them apart as trails.
In America, where urban sprawl has begun to strike even the most rural communities, developers and local leaders are currently striving to make their communities more conducive to non-motorized transportation through the use of less traditional "trails." The Robert Wood Johnson Foundataion has established the Active Living by Design program to improve the livability of communities in part through the through trails, both in a more traditional sense, as is being done by the Upper Valley Trails Alliance or in the broader, as is being done by Groundwork Somerville .
The term "trail" has also been used by developers and urban planners for a variety of modern paved roads, highways, and boulevards. A particularly unusual use of the term is in the province of Alberta, Canada, which has multi-lane freeways called "trails."
While many trails have arisen through common usage, quality trail design and construction is a complex process requiring certain sets of skills.
When a trail passes across a flat area that is not wet, often all that is required is to clear brush, tree limbs and undergrowth to produce a clear, walkable trail. When crossing streams, bridges may or may not be desirable, depending on the size of the stream and the depth of its banks. In wet areas, it may be necessary to create an elevated trailway with fill or by building a boardwalk. One problem with boardwalks is that they require frequent maintenance and replacement - boards in poor condition are often slippery and hazardous.
Trails on slopes
A common mistake in establishing trails is to make them on slopes that are too steep for comfort and the environment. Such steep trails generally result in serious erosion, a wide swath of impacted area as walkers go to the sides to find better footing, and the inability of many hikers to walk the trail. An absolute limit for trail grades is a slope of one in six, and a more practical limit is a slope of one in eight. Trails that ascend steep slopes may use switchbacks (also called hairpins), but switchback design and construction is a specialized topic that takes great care. The best trail designs eliminate switchbacks.
If a trail is being made to be accessible to off-road wheelchairs, the slope should be no more than one in ten. If a paved trail has to be accessible to all wheelchairs, the slope must be no more than one in twelve, with periodic level pulloffs.
The off-slope, or side-slope, of the trail also must be considered. This is the slope of the trail from side to side, and should never be more than one in twelve. Side-sloped trails are prone to gullying. Ideally, the treadway of the trail should be almost, but not quite, level in cross-section.
Achieving the proper slope in hilly terrain usually requires the excavation of sidehill trail. This is trailway that is constructed by establishing a line of suitable slope across a hillside, then digging out by means of a mattock or similar tool to create the trail. This may be a full-bench trail, where the treadway is only on the firm ground surface after the overlying soil is removed and 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 problem areas, it may be necessary to establish the trail entirely on fill. In cases where filling is used, it's necessary to pack it firmly and to revisit the site periodically to add to the fill and repack it until fully stable.
An important and often-overlooked factor in trail construction is that of drainage. 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 issue. Trails, by their nature, tend to become drainage channels and eventually gullies if the drainage is not properly controlled.
In areas of heavy water flow along a trail, it may be necessary to create a ditch on the uphill side of the trail with drainage points across the trail. The cross-drainage may be accomplished by means of culverts, which must be 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. Using timbers or rocks for this purpose also creates erosion barriers. Rock paving in the bottom of these channels and in the trailside ditches may help to maintain stability of these. Ideally, waterbars should be created, with or without ditching, at major points of water flow on or along the trail, and in conjunction, if possible, with existing drainage channels below the trail. Another important technique is to create coweeta dips, points on the trail where it falls briefly (for a metre or so) and then rises again. These provide positive drainage points that are almost never clogged by debris.
Trails intended for use by bicycles, wheelchairs and pedestrians will often be surfaced, especially in heavily-used or urban areas. This can be asphalt paving, or compressed stone dust . Such trails will also have well-built bridges with a supported deck and side rails.
For long-distance trails, or trails where there is any possibility of anyone taking a wrong turn, blazing or signage should be provided. This may be accomplished by using either paint on natural surfaces or by placing pre-made medallions. Generally speaking, every trail should have a distinctive blaze, of a particular color and shape. Horseshoe-shaped blazes are good for bridle trails (but be sure to have the "u" of the horseshoe opening to the top, or you'll offend some riders!). The Appalachian Trail is blazed with white rectangles. Blue is often used for side trails.
When using paint on trees, the preferred technique is to use a drawknife to smooth the outer bark of trees without penetrating to the inner bark (so as to not injure the tree), then using an oil-based paint to create the blaze. Stencils are often useful, and sash brushes are the preferred brush type for precise work. Oil-based paint seems to last longer than latex-based and seems to be more benign to the bark. Blazes may also be painted on obvious rock surfaces or on posts set into the ground (or on utility poles, fences, or other handy surfaces). In higher alpine areas, where no trees are available and painting on rocks would not last, stacks of rocks called "cairns" are used to mark the path.
A very common and major error in building trails is assuming that once a trail is built, it needs no further work. Nothing could be further from the truth. Not only does a trail need annual clearing work to remove vegetation, fallen wood and other obstacles, but often needs minor or major regrading work from year to year, and often drainage improvements and erosion control, not to mention marking and signage.
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