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Steps to Follow

Construct trails in a manner that will enhance the user's outdoor experience while protecting the property's environmental health. Trail design and construction require planning. The following steps will help you complete a successful trail-building project.

• Step 1. Decide the trail's purpose
• Step 2. Inventory the property
• Step 3. Design the trail
• Step 4. Scout the trail corridor
• Step 5. Clear the trail
• Step 6. Construct the trail tread
• Step 7. Mark the trail

STEP 1. DECIDE THE TRAIL'S PURPOSE
Different recreational activities require different trail designs. Besides recreation, your trail also may provide access for fire protection, timber harvesting, boundary marking, and other woodland management activities.

The extent to which trail uses can be mixed depends on your objectives, the number of users, and the type of activity. Some activities, such as snowmobiling and cross-country skiing, require separate trails. Other activities are compatible on the same trail or occur in different seasons.

To decide the trail's purpose, identify desired recreational uses and a general project area. Base decisions on the property's physical resources and your long-term ownership goals. Technical assistance for evaluating your resources, generating management alternatives, and preparing a woodland stewardship plan is available from many sources, including the state department of natural resources foresters and wildlife managers, soil and water conservation districts, private consultants, and county extension service offices.

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STEP 2. INVENTORY THE PROPERTY
Examine the project area for natural and constructed features that will enhance or detract from the trail user's experience. They can be used to identify key places that the trail should connect (e.g., vistas, hunting and fishing areas, meadows, forest management projects) and fragile areas that should be avoided or that will require extra care (e.g., steep slopes, gullies, waterways, wetlands, erodible soils, rock outcrops, historic places). Also note the location of existing roads and trails that might be incorporated into the trail design. Gather this information on a map of the property drawn approximately to scale.

Topographic maps are a valuable resource for trail layout. They can help you identify potential routes, problem areas, scenic overlooks, public roads, and water crossings. Obtain maps from bookstores or by writing the U.S. Geological Survey, Map Distribution, Federal Center, Building 41, Box 25286, Denver, CO 80225 (tel. 1-800-USA-MAPS). Request maps with a scale of 1:24000 (1 inch = 2,000 feet).

Aerial photographs, another valuable tool, are available at most local USDA Agricultural Stabilization and Conservation Service offices. They are especially useful in locating existing roads, vegetative cover types, watercourses, and land uses.

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STEP 3. DESIGN THE TRAIL
Develop design specifications for your trail based on its intended use. Determine the trail pattern and approximate length, maximum grade and curve radius, and minimum overhead clearance and width standards. Carefully examine the area for routes between points of interest. Identify potential trail-use hazards or construction problems, including lakes and streams, motorized roadway intersections, and soils that are erodible or poorly drained.

Vary trail patterns to fit the trail's purpose and the property's physical attributes (figure 1). Try to develop a trail pattern that connects your points of interest in a closed loop design with a single access point. Loop patterns avoid the backtracking requirement of linear trails and allow you to incorporate more trail miles into a small area. You can design the loops with internal cutoff trails to offer different travel lengths and user experiences. Use linear trails for traversing long distances, connecting existing trails, and accessing out-of-the-way areas off the main loop (e.g., summits, waterways).

Locate trail entrances carefully to encourage use but reduce vandalism. Minimize the number of trail access points. Use a single entry/exit point to reduce user confusion and increase your control of trail access. If the entrance and exit cannot be at the same point, locate the exit within sight of the entrance. However, screen the exit from the trail to ensure that users do not take shortcuts prior to reaching it.

Use a short linear trail to access loop trails. Try to locate the access trail on level terrain because steep climbs or drops may discourage potential trail users. Select a loop direction that allows users to traverse a majority of the climbs in the first half of the trail before they tire. Reverse curves and barriers can be used to ensure that trail traffic flows onto the loop in the desired direction (figure 2).

Determine trail length based on general user expectations and abilities, your property's physical characteristics, and type of recreation. In many cases trail development can be coordinated with neighboring properties to obtain additional length. Suggested trail lengths for each activity are reported in Recommended Trail Standards.

Incorporate curves and subtle bends into the trail design to increase user interest and promote an atmosphere of remoteness. Straight sections rarely should exceed 100 feet. This rule may be broken when trails cross open fields, motorized roads, waterways, or potential hazards. Trail users may become lost or leave the trail when crossing an open field. To avoid these problems, select the most direct route, or parallel a woodland edge or fencerow. Maintain adequate sight distances (see Recommended Trail Standards,) when approaching a potential trail hazard and always cross waterways and motorized roads at a 90-degree angle.

Exercise caution when designing trails for cross-country skiing, snowmobiling, and bicycling. The minimum turning radius must increase with the speed of the trail user. Try to maintain a forward sight distance of 100 feet on snowmobile and bicycle trail curves. Avoid placing curves on downhill slopes or at the bases of hills. End downhill runs with a straight section on level terrain that is at least as long as the slope or with a short rise in grade before entering a curve. If a downhill curve is necessary, install warning signs at least 100 feet prior to entering the curve and provide a runout or widen the trail or increase the turn radius (figure 3). Provide wider curves with longer sight distances on heavily used trails with traffic flowing in both directions.

Grade is a measurement of trail slope generally expressed as a percentage. Percent grade is equal to vertical distance divided by horizontal distance times 100. For example, an 8 percent grade is one that goes up or down 8 feet for every 100 feet of length. Acceptable trail grades depend on the recreational activity and soil structure. Table 1 describes different trail grades. A sustained grade (any grade that remains the same for more than 1,000 feet) generally should not exceed 10 percent, although this limit may be exceeded for short distances (50 yards) up to a maximum of about 25 percent. Consult your local Soil Conservation Service office for detailed soil information. Loam soils with a mixture of sand, silt, and clay generally sustain trail traffic on steep slopes better than soils with sand, silt, or clay alone. Trail grades can be measured on the site using a clinometer. (See How to Make a Clinometer,)

Table 1. Description of Different Trail Grades.
Percent Grade	Description
0 to 2 3 to 6 7 to 12 13 to 18 19 to 25 26 and greater	Nearly level Gently sloping Moderately sloping Moderately steep Steep Very steep

Long, steep grades tire trail users and allow drainage water to flow down the trail creating potential erosion problems. Conversely, level grades tend to bore trail users and allow water to accumulate on the trail bed. To facilitate natural drainage and increase user interest, frequently alternate steep and level grades. As a rule of thumb, trails should be 1/3 level, 1/3 uphill, and 1/3 downhill. Switchbacks or steps may be necessary to traverse steep slopes (figure 14 and figure 15).

Trail width and overhead clearance standards depend on the trail activity, terrain, and maintenance needs. A trail corridor normally is cleared to a minimum height of 8 feet and a width of 4 to 6 feet (figure 4). Smaller clearings often are quickly closed by growing vegetation. This especially is true where trails pass through dense brush. Expand the clearing width as the trail approaches a motorized roadway crossing to ensure adequate sightlines, especially if the user's pace is faster than walking. Different clearing widths and heights may be used to encourage a variety of trail vegetation and reduce the tunnel effect created by clearing a corridor through dense brush. Additional clearance also may be necessary to compensate for branches sagging with heavy snow or rain. As a general rule, clearing width increases with a trail user's speed. Provide additional clearance on downhill sections and turns.

Narrow clearings may be used on uphill climbs to help reduce erosion. However, cross-country ski trails must be wide enough (10 to 12 feet) for users to "herringbone" or "sidestep" on uphill climbs and to "snowplow" on downhill runs. Determine the clearing width required for trail maintenance vehicles and ski trail grooming equipment. Tractors and trucks require a minimum clearing width of 8 feet with additional space provided on turns.

Lakes, rivers, streams, and wetlands need protection from potential erosion problems. Avoid trail routes that directly adjoin the water's edge. Favor natural benches or terraces located above the ordinary high water mark (figure 16). Maintain vegetative filter strips between the trail and the water. The width of a filter will vary depending on the slope of the land between the water and the trail (table 2). Occasional spur trails may be used to access the water's edge. Physical barriers or vegetative screening may be necessary to discourage short-cutting to the water.

Keep stream crossings to a minimum. Consider developing loop trails on both sides of the stream with a single crossing. Locate bridge crossings where the stream is narrow. Locate fords where the stream is shallow. Avoid crossings where the stream bends or has unstable banks because of potential soil erosion. Make stream crossings at a 90-degree angle with a straight, level approach (figure 5). The length and grade of the approach depend on the speed and stopping ability of the trail user. Permits from your state department of natural resources and/or the U.S. Army Corps of Engineers may be required before constructing any stream crossing, including fords.

Table 2. Filter Strip Width Guide for Trails.
Land Grade Between Trail and Body of Water (percent)	Recommended Filter Strip Width (feet)
0 to 1 2 to 10 11 to 20 21 to 40 41 to 70	25 30 to 50 51 to 70 71 to 110 111 to 170

Motorized roadway intersections endanger trail user safety and detract from the outdoor experience. Identify alternative routes and patterns that reduce the number of crossings. If a crossing is necessary, avoid locations that are at the base of a hill on the trail or near a curve in the road. Use straight, level (less than 5 percent grade) approaches and post warning signs 100 feet prior to the crossing. A crossing must be made at a 90-degree angle to the road with minimum sight distances maintained in both directions for vehicle drivers and trail users. Minimum sight distances for motorized vehicles on the roadway are 800 feet at highway crossings, 500 feet at county roads, and 400 feet at local roads. On both sides of the intersection, develop V-shaped, funnel openings to the trail that are at least twice the trail's normal width.

Soil types affect water drainage, erosion potential, and tread material. Use soil maps to identify the location of soil types in your woodland and determine their suitability for different uses and structures. Soil maps are available at most local USDA Soil Conservation Service offices and some libraries. However, this information should be supplemented with an on-site examination of the area. Your local USDA Soil Conservation Service can help you evaluate soils along the trail route and recommend protective measures. When possible, avoid placing a trail on flat, low-lying terrain and slopes exceeding 10 percent where water drainage problems and erosion may occur.

Soil surface and subsurface color can be used to evaluate soil drainage. A uniform soil color (yellow, brown, red) usually indicates adequate drainage. However, if the soil is gray or olive colored with some mottles (spotted with concentrations of red, yellow, brown, or bluish-gray soil), drainage may be poor.

Examine the trail area for excessive surface water during the spring thaw or after a heavy rain. To test soil drainage, dig a hole 18 inches deep and 4 to 6 inches wide, and fill it with water. Once the water has completely drained, fill it a second time. If the water fails to drain from the hole within 18 hours (1 inch per hour), the soil either is poorly drained or has a high water table. (Do not use this test when the ground is frozen or after a heavy rainfall.) Avoid these areas, especially if the depth to the water table, bedrock, or hard clay is less than 20 inches. Shallow soils not only have drainage problems, but also tend to erode easily and may slide when walked on. Favor locations where soil depth exceeds 3 feet.

Table 3. Soil Textural Classes.
Soil Texture	Identification
Sand	Loose and gritty. Will not form a ball.
Loam	Smooth (flour-like), but slightly gritty. Forms a ball, but ribbon usually breaks easily.
Silt	Smooth like flour, no grittiness. Forms ribbon that breaks under its own weight.
Clay	Smooth and sticky when wet. Forms ribbon that is long and pliable.
Organic (peat, muck)	High amount of decomposed material and water. Black to brown color. Wetlands, low areas.

Soil texture has a major influence on soil drainage and erodibility. Texture refers to the sizes of individual soil particles. Clay and silt are the smallest particle sizes, and soils containing high amounts of these particles tend to be muddy when wet or cracked and dusty when dry. They are susceptible to compaction and are highly erodible, especially on steep slopes. Likewise, soils composed mostly of sand, which has the largest particle sizes, are extremely unstable and should be avoided. Single-texture soils may be suitable for trail use if gravel-sized particles are embedded in the soil. The best soils for trail use are loam soils that contain a mixture of sand, silt, and clay. Boardwalks or corduroy may be required on trails built on sand or clay soils. (See Subsurface Drainage.)

To identify a soil's textural group, moisten a small amount of soil to the consistency of putty. Make a small ball of soil and squeeze it between your thumb and forefinger, pressing the thumb forward to form the sample into a ribbon. Table 3 describes each soil by textural class.

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STEP 4. SCOUT THE TRAIL CORRIDOR
Walk the proposed trail corridor in both directions using a compass and map. Identify potential problems (e.g., steep slopes, water and motorized road crossings, wet soils, rock outcrops) and develop solutions. (See Handling Trail Obstacles.) In late spring, when the leaves are off the trees and the ground is free of snow, examine trail drainage and vegetative screening between trails. A trail that follows natural contours, gently curving and bending around obstacles, and that disturbs the site as little as possible, is aesthetically pleasing and more enjoyable to travel. It may be necessary to adjust the route several times. Once the final location has been determined, mark the route with brightly colored plastic flagging tape tied to trees and shrubs.

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STEP 5. CLEAR THE TRAIL
Begin construction by removing trees, brush, and rocks from the tread. Establish a trail clearance width and height according to the intended use. (See Recommended Trail Standards, page 19.) Site characteristics and trail length will determine what tools are needed. Hand tools, such as axes, loppers, bow saws, weed whips, and chain saws, will be sufficient in most cases. A small bulldozer, brushmower pulled by a tractor, or a log-skidder with a blade, is appropriate for clearing long, wide trails on stable soils. The trail can be cleared much faster with motorized equipment, but extreme care must be used to protect the trail bed and surrounding vegetation.

Cut shrubs and small trees flush with the ground to prevent tripping and to reduce stump sprouting. Avoid cutting healthy trees larger than 7 inches stem diameter. Some trees, such as boxelder, elm, hickory, and basswood, may require chemical stump treatments to prevent re-sprouting. Prune overhanging branches cleanly at the branch collar (figure 6) on the tree trunk or where a branch forks. To avoid rapid regrowth, it may be better to remove small trees than to cut off their tops. Remove large rocks and fallen logs from the trail, unless they are to be kept as obstacles to prevent motorized use. Scatter branches and other debris off the trail or pile it for wildlife cover.

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STEP 6. CONSTRUCT THE TRAIL TREAD
For most trails, the ideal surface is natural soil free of stones, stumps, and protruding roots. Natural trails often become easily distinguishable and comfortable to walk after a month of regular traffic. Always avoid unnecessary disruptions of the ground surface. If leveling is required, use a shovel or small caterpillar (D-2 or equivalent) to sheer off a thin layer of topsoil, level humps, and fill holes. Gravel or other fill materials may be used to elevate the trail in wet areas. (See Subsurface Drainage.)

A 3- to 6-inch layer of woodchips, shredded bark, or sawdust can increase hiking comfort and reduce soil compaction. These materials often can be obtained at little or no cost from local utility companies, yard waste recycling centers, and sawmills. However, they tend to decay quickly in a shaded environment and must be replaced at least every two years. Woodchips also can interfere with water drainage and may wash off slopes that exceed a 5 percent grade.

Vegetative coverings, such as grasses and legumes, should be favored because they reduce soil compaction and erosion and help retain snow coverings on cross-country skiing and snowmobiling trails. With periodic resting periods, vegetation recovers well from heavy use. Species selection varies widely depending on the amount of light and type of soil. Generally it is best to plant a mixture of species. Contact your local department of natural resources or soil and water conservation district for information on specific species and application procedures.

Use hard surfaces only for heavily used trails, wheelchair-accessible trails, and touring bicycle trails. Commonly used surfaces include soil cement (a mixture of cement and sandy soil), granular stone (crushed limestone or sandstone), asphalt, and concrete. These materials can be extremely expensive to purchase and install. Professional assistance is recommended.

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STEP 7. MARK THE TRAIL
Once constructed, a trail should be marked so that its route is clear in any season of the year. Trail markers may be paint blazes, plastic or metal markers fastened to trees, wooden posts with directional arrows, rock cairns, or reflective tape for night use (figure 7). As a rule, trail users should not travel more than 600 feet without being able to see a trail marker or sign. On poorly cleared trails, users should be able to sight from one trail marker to the next. If a trail has two-way traffic, travel it in one direction placing markers at appropriate locations, then travel it in the opposite direction and place additional markers as needed.

Paint blazes usually are applied with a paintbrush or spray can to trees or rocks at a height of 5 to 6 feet above the ground. Apply a double blaze, one blaze 2 inches above the other, at critical junctions and obscure turns to warn trail users to pay attention. Select a color that stands out well in your woodland; blue, yellow, orange, red, and white are commonly used. If your trail is open to the public by agreement with a public agency, contact that agency for advice about which color to use. Oil-based enamels and inks tend to outlast water-based paints. Before applying the paint, smooth and clean rough-barked trees with a paint scraper, but do not cut through the protective bark. Clean rocks with a wire brush.

Metal or plastic trail markers about 3 to 4 inches square may be substituted for paint blazes. They can be fastened to trees with nails. Let the nail protrude an inch or two from the tree to allow the trail marker to move outward as the tree grows in diameter.

For night hiking, fasten two reflector tape ovals (cateyes) to a small board and attach these markers to trees at close intervals for easy detection with a flashlight.

In treeless areas, fasten trail markers to wooden posts. Directional arrows also may be needed. Anchor direction posts with an underground brace to ensure that they are not twisted. Where wooden posts are not available or practical, mark the trail with rock cairns.

Trail signs may be needed, especially if your trail is open to the public or large numbers of visitors. Entrance signs should identify trail names, trail marker colors, distances or travel times between major trail junctions, potential hazards, places of interest, and the types of trail uses permitted (figure 8). At trail junctions you may need a sign that shows trail users where they are at in the trail system or the distances to the next junctions, but simple direction posts are more common. Post hazard signs at least 100 feet prior to all water crossings, motorized roadway intersections, and steep dropoffs. Use consistent, concisely worded sign designs. Keep the number of signs to a minimum as they detract from the user's outdoor experience and are frequent targets for vandalism and theft. Make signs at least 12 inches by 12 inches and use contrasting colors for the background and lettering. Mount signs at a visible height (4 to 5 feet above the ground) on sturdy (4-inch top), rot-resistant posts. To be rot-resistant, posts should be treated with oil-soluble chemicals or waterborne salts. Waterborne salts, such as chromated copper arsenate (greenish tint), are recommended because of their cleanliness and low toxicity to plant roots.

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Handling Trail Obstacles

Along the trail route you may encounter an obstacle that requires special attention. Recognizing and protecting such areas during construction will help reduce later maintenance costs and potential environmental damage. Some methods are relatively simple and inexpensive; others can be extremely difficult and expensive. Carefully evaluate alternative trail routes and consult with a professional.

SUBSURFACE DRAINAGE
Water tends to pool on trails that are located on low-lying, level terrain. Raising the treadway 3 to 6 inches (or more) above the surrounding terrain will allow water to drain away, reduce maintenance costs, and ensure comfortable trail use. Use gravel, flat stones, fabric mats, corduroy, or boardwalks to elevate the trail surface (figure 9). Boardwalks and corduroy also may be used on erodible soils such as sand or to protect soils with exposed tree roots from additional damage. Another option, log bridges, is discussed in the section on Stream Crossings, figure 18.

A less expensive technique for moving water off the trail is center crowning. Fill materials can be obtained from drainage channels or gutters cut on both sides of the trail to facilitate drainage (figure 9).

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SURFACE DRAINAGE
On steep slopes, poorly designed and constructed treadways allow water to accumulate, gain downhill velocity, and erode the trail. Flowing water must be diverted off the trail. One effective method is to outslope the trail surface at a 2 to 3 percent grade toward the downhill side. (figure 12 shows outslope.) Grade dips or waterbars also may be used. Grade dips are short trail sections cut at a grade opposite that of the prevailing trail surface (figure 10). Grade dips typically are established at natural drainageways or ditches with intermittent flows.

Waterbars are obstructions on the trail surface designed to divert water off the trail. They usually are constructed with logs or stones placed at a 30-degree angle from the trail's edge. Such waterbars must extend well beyond both sides of the trail to prevent water or people going around them (figure 11). Logs must be at least 6 to 8 inches in diameter and obtained from rot-resistant species, such as cedars, white oak, bur oak, and black locust. Open-top culverts (figure 17) or earthen waterbars also may be used.

Table 4. Waterbar Spacing for Trails.
Percent Grade	Spacing Between Waterbars (feet)
2 5 10 15 25+	250 130 80 50 40

Rubber water deflectors constructed with old conveyor belting reduce potential waterbar hazards to bicyclists.

Increase the number of waterbars as the trail's grade increases (table 4). Provide additional waterbars near hilltops because early water removal is critical on steep slopes.

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HILLSIDE TRAILS
Hillside cuts are difficult to construct and often require professional assistance. Figure 12 shows two techniques for constructing a hillside trail base - full bench and cut-and-fill. Backslope cut ratios vary depending on the soil (table 5). On most hillsides a 1:1 (horizontal:vertical) backslope cut ratio is acceptable. Take precautions to ensure that water does not flow down the trail and cause erosion. Cross-trail drainage can be encouraged by maintaining a 2 to 3 percent outslope on the treadway. Avoid unnecessary disruptions to the natural vegetation beside the trail and always attempt to protect large trees. Establish native vegetation, grasses, or legumes on exposed soils.

Table 5. Backslope Cut Ratios by Soil Type.
Soil Type	Backslope Cut Ratio (horizontal:vertical)
Sand Moist clay Loose, gravelly soil or organic Loose rock Stable rock	3 or 4 : 1 2 or 3 : 1 1.5 or 2 : 1 0.5 : 1 0.25 : 1

A retaining wall may be required to protect the trail base when the sideslope grade exceeds 50 percent (figure 13). Stones or rough-sawn, rot-resistant timbers may be used to construct the wall. Water must be allowed to drain around, beneath, or through the wall and must not be allowed to accumulate behind it. Professional assistance is recommended.

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STEEP GRADES
If trails must traverse steep slopes to access important places, switchbacks or steps may be required. Both have considerable drawbacks and alternative routes should be carefully evaluated. Professional assistance is highly recommended.

Switchbacks are designed to reduce trail grades by lengthening the trail (figure 14). Trail grades rarely exceed 10 to 15 percent. Switchback turns (or landings) must be located on stable soils to reduce erosion. Favor flat benches or areas with the least slope. Timber steps may be used to level the landing and reduce erosion. A minimum turning radius of 4 feet is required for hiking trails; 8 feet is required for other trail users. Shortcut trails often develop prior to switchbacks. Construct log, rock, or shrub barriers at trail turns to ensure that users remain on the trail. Alternatively, attractive features such as benches and vistas may be located at the turn.

Steps may be needed on steep terrain with highly erodible soil, but have several drawbacks. They may be costly to construct, restrict trails to summer use, and prohibit access for some disabled persons. Construction materials for steps include stone slabs, railroad ties, or rough-sawn, rot-resistant timbers (figure 15). Steps should rise at least 5 inches, but not more than 9 inches. Stairways may be required on slopes exceeding 100 percent (45 degrees).

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STREAM CROSSINGS
Many trails eventually cross a drainage ditch or small stream. Before initiating any project, contact your local department of natural resources hydrologist to determine if the trail crosses a protected water or wetland. State jurisdiction over the use of protected waters and wetlands generally begins at a point known as the ordinary high water mark (figure 16). Permits from the Army Corps of Engineers and/or your local department of natural resources may be required before constructing any crossing, including fords. Some local governments impose additional restrictions. In Minnesota, any project constructed below the ordinary high water mark that alters the course, current, or cross-section of protected waters or wetlands is subject to regulatory jurisdiction of the Department of Natural Resources (statute 105.42).

Fords (or natural crossings) often can be used to traverse slow moving streams less than 24 inches deep. Favor locations with gently sloping, stable banks and gravel or sand bottoms. Most hikers can safely negotiate a crossing on flat stones placed at convenient intervals. Stones should be large enough for the surface to remain dry with 1/3 to 1/2 of their height embedded in the streambed. Gravel or natural rock also may be used to improve the streambed for vehicle and horse travel. Stream banks may be graded to permit safe passage into and out of the ford and to keep water from running down the trail. Finished banks should be no steeper than 5:1 (horizontal:vertical), and must be seeded or mulched to reduce erosion.

Culverts can be used to cross deep streams or ditches (figure 17). To prevent trail washout, always install culverts that are wide enough to accommodate the greatest expected water flow. (Culverts generally are sized to accommodate the maximum water level of a 25- to 50-year flood.) Align culverts with the channel to reduce bank erosion and debris accumulation. Some excavation may be necessary to obtain a firm foundation in the waterway. Cover metal culverts with fill that is at least 1/2 the pipe diameter (1 foot minimum) in depth to prevent puncture. On shallow ditches, rock or log culverts may be preferred because they blend in well with the natural trail appearance and can be built from materials at the site. Consult with your local soil and water conservation district if you plan to use a culvert. They can advise you about its size, location, design, and installation.

Bridge designs vary depending on the length and height of the crossing, type and amount of trail use, and size of maintenance equipment. On hiking trails, a simple log bridge may be used for stream crossings less than 10 feet wide (figure 18). Favor locations with stable soils that offer a relatively level bridge surface between both banks. Always locate bridges above the ordinary high water mark. Anchor small bridges or cable them to large trees at one end so they can swing away during flooding. Install handrails on bridges higher than 2 feet above the water, or that cross deep or fast moving water.

Wider streams will require permanent bridge designs, such as the outrigger bridge (figure 19). Professional design assistance and regulatory permits almost certainly will be required. Construct permanent bridges with rot-resistant timbers and non-corrodible fasteners that protect water quality and blend with the trail's natural appearance. You may be able to purchase a prefabricated bridge that breaks into sections for transportation.

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FENCE CROSSINGS
A self-closing gate or stile will reduce fence damage and permit safe crossing (figure 20). Stile designs vary depending on the size of the livestock and the availability of building materials. Construct stiles with sturdy, rot-resistant timbers. Cover electric fences with a section of plastic hose and use pliers to twist off wire fence barbs.

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DAMAGE
A certain amount of vandalism, as well as accidental damage, can be expected on heavily used trails that are open to the public. Damaged items, if not promptly removed or repaired, stimulate more damage. Inspect your trails regularly and identify problem areas early.

Proper trail design methods can reduce damage. Select trail routes that avoid sensitive environments. When possible, keep the trail at least 10 feet away from smooth-barked trees (e.g., birch, aspen, beech). Use brush piles, drainage ditches, or vegetation (e.g., rose, raspberry, blackberry, gooseberry) to keep people on the trail. These methods, unfortunately, detract from the outdoor experience and can increase the amount of accidental damage when users leave the trail to examine attractive sights. If accidental damage is occurring, it may be wise to route the trail closer to the site and thus eliminate the need to leave the trail. Trail signs also can be used to encourage compliance. However, it is important to avoid the use of negatively worded signs. Words such as "don't" not only challenge vandals, but also identify potential targets. When space permits, explain the reasons for protecting the area. For example, "Prevent erosion, please stay on trail."

Vandalism tends to occur near a trail entrance. To reduce vandalism, locate signs, benches, and other attractive targets at least 500 feet inside the trail. A V-shaped clearing in the vegetation can be used to identify the entrance and funnel users onto the trail. Screen parking lots and trail entrances from passing roads, or locate them in areas where access can be monitored. Vehicle barrier posts or gates may be required at trail entrances or bridges. Favor barriers that can be removed to permit access for emergency vehicles and maintenance equipment. Avoid potential safety hazards by clearly marking all barriers and gates with bright orange paint, reflectors, or reflective tape. Your local department of natural resources may be able to recommend methods for reducing damage and selecting resistant construction materials.

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Recommended Trail Standards

Hiking

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• Trail Layout
  Trail patterns vary depending on the expectations of the trail user. Day users tend to favor a loop or a series of loops. Design trails to cover a variety of vegetation, land forms, and sights. Frequently occurring curves and grade changes will add interest. Short spur trails may be used to access waterways and summits.

• Length
  Hikers travel at 1 to 3 miles per hour depending on the terrain and their ability. Hiking trails should be long enough to afford a meaningful recreational experience and short enough to suit a hiker's ability. Internal connector trails and cutoffs can be used to offer different trail lengths.

  Day use:	1/4 to 5 miles (1/2 day) 5 to 15 miles (full day)
  Backpacking:	25 or more miles

• Clearing Width
  Vary clearing widths to avoid the tunnel effect and promote a variety of trail environments such as woodland flowers, meadow openings, and woodland edges. Trails generally should narrow on steep slopes to a minimum width of 3 feet.

  Light use:	4 to 6 feet (one-way traffic)
  Heavy use:	7 to 10 feet (two-way traffic)

• Clearing Height
  8 feet. Additional clearance may be needed to compensate for extended backpacks and branches drooping with heavy rain or snow.

• Tread Width
  

  Light use:	2 to 3 feet (one-way traffic)
  Heavy use:	4 to 6 feet (two-way traffic)

• Trail Surface
  

  Light use:	Natural with gravel or corduroy used in wet areas
  Heavy use:	Natural if possible; woodchips or gravel

• Turning Radius
  Turning radius is not critical; however, gentle curves are aesthetically pleasing and easier to maintain. Shortcut trails often will develop prior to sharp-angled turns. Straight sections usually should not exceed 100 feet.

• Percent Grade
  Grades exceeding 10 percent are difficult for hikers to sustain and, without additional protection, erosion problems often will develop. Steps, switchbacks, or waterbars may be needed on slopes over 25 percent. Occasional grade changes and dips should be incorporated into the trail layout to promote user interest and facilitate natural drainage.

  Desired:	0 to 5%
  Maximum:	15% (sustained) 40% (shorter than 50 yards)
  Outslope:	4% (maximum)

• Sight Distance
  Sight distances are not especially critical on hiking trails. However, motorized road crossings must be carefully located and designed to ensure that trail users and vehicle drivers have good sight distances in all directions.

• Water Crossings
  Structures for crossing water depend on the flow and length of the crossing and expectations of the hiker - almost all methods will accommodate foot traffic.

  Bridges:	Must be located above ordinary high water mark or cabled at one end to prevent washout. Width: 2 to 4 feet (light use) 5 to 6 feet (heavy use) 8 feet or more (maintenance vehicles) Weight capacity: Variable depending on maintenance equipment, bridge length, and alternative trail uses
  Fords:	Slow moving water less than 24 inches in depth may be forded. Rocks and stepping stones may be used to assist hikers.

• Compatible Uses (with additional trail design standards)
  

  Winter:	Snowshoeing, ski touring, or snowmobiling
  Summer:	Horseback riding (low use), or accessibility trails for persons with disabilities

• Facilities
  Parking area, picnic area, resting areas, overlooks, campsites, water, information board, signs

Table of Contents TRAILS SIMILAR IN DESIGN TO HIKING TRAILS Hunting and Nature Viewing Trails Hunting and nature viewing trails generally are designed to accommodate a low number of users. Trail patterns should focus attention on the food, water, and cover your woodland provides for wildlife. Learn about the habitat requirements of different wildlife species. Keep in mind that these requirements often fluctuate seasonally. Habitat improvement measures may be necessary to attract desired species. Contact your local department of natural resources wildlife manager for technical assistance and cost-sharing information. Select trail routes that pass through a diversity of wildlife habitats. Aerial photographs offer a valuable tool for locating different vegetation types and ages, openings, and waterways. Areas between adjoining habitat types tend to offer the greatest species diversity. Uplands between wetlands or waterways are excellent trail locations. Examine the site carefully for deer trails or other wildlife travel routes. Constructed trails often will be used by wildlife. Carefully select vantage points near openings or waterways. Water, especially if it is running or splashing, attracts birds and other species. Avoid routes that cut across open meadows or fields. Woodland edges should be favored. An occasional cut into the open area may be used to observe the forest canopy. Ridges provide excellent spots for viewing birds that inhabit upper parts of the forest canopy. Avoid routes that traverse sensitive nesting and rearing areas (e.g., blue heron rookery). Design the trail to approach prime viewing areas with the sun at the trail user's back. This helps illuminate birds and other wildlife for easy viewing. Incorporate gradual curves into the trail design. Keep the trail surface as natural as possible, with woodchips, corduroy, or gravel added only in wet areas. Clear trail corridors 3 to 4 feet wide and 6 to 8 feet high. Narrower trails are quickly closed by surrounding vegetation. When safety permits, dead standing trees (commonly known as snags) should be retained as they offer homes and feeding locations for many bird and mammal species. Consider erecting nest boxes or creating artificial snags in woodlands near the trail route. Your local wildlife manager can assist you in locating and designing hunting and nature viewing trails. Table of Contents Canoe Portages Canoe portages must be carefully located to ensure that the shortest, easiest route is selected. Place landings on stable soils in areas of slow moving water. Level, sandy approaches are preferred. (Permits may be required before improving any canoe landing.) Clear portage trail corridors 6 feet wide and 12 feet high. Provide additional clearance for negotiating curves. Natural surfaces are recommended; corduroy, gravel, woodchips, or boardwalks may be added in wet areas. Most canoeists favor 0 to 5 percent grades, but can negotiate 20 percent grades for short distances. Switchbacks and waterbars may be needed on steep slopes. Stairs are not recommended. Place canoe resting bars at intervals of about 275 yards on long trails (figure 21). Table of Contents Accessibility Trails for Persons with Disabilities Hiking trails often can be made accessible to persons with physical disabilities. Recognize the types and needs of disabled persons before designing the trail. Their outdoor expectations differ little from other trail users. When designing the trail, work closely with potential future users and local groups representing persons with disabilities. Encourage input from persons with a variety of disabilities, including sight, hearing, mental, heart or lung disease, and ambulatory limitations. In many cases, simple steps can be taken to ensure access. For additional guidelines on accessibility trails, refer to the Americans with Disabilities Act. Loop trails with cutoffs are desirable. Although trail lengths of less than 3/4 mile often are provided, a variety of trail lengths are needed to accommodate different abilities and expectations. Identify routes with a variety of different sights, sounds, odors, and objects. Trails should follow a logical sequence to prevent the user's loss of direction. An able-bodied guide should not be required. Place a trail information sign at the entrance. Mount it within easy reach of the trail at a height of 30 to 40 inches. Use raised or routed letters to inform users about the length and difficulty of the trail and the locations of rest stops, cutoffs, and potential hazards. Trails should be free of debris and cleared to a width and height of 8 feet. On trails with one-way traffic, most treadways should be at least 3 feet wide; 5 feet on two-way traffic trails. For wheelchairs, blacktop is almost a necessity for the trail tread, but flagstones, bricks (gaps less than 3/8 inch), or crushed rock that has been rolled and compacted also may be used. Provide boardwalks in wet areas. Visually handicapped persons can use natural trail treads with guide ropes or definite edges such as logs or railroad ties. Although trails usually are located on level terrain with grades rarely exceeding 5 percent, acceptable grades will vary depending on the abilities and expectations of trail users. Provide regular rest stops on steep slopes. Always avoid motorized roadway crossings and obtain professional assistance when locating and designing bridges and boardwalks. Bridge and boardwalk decks must be flush with the trail surface and handrails should be installed. Position decking boards perpendicular to the trail path with gaps between boards not exceeding 3/8 inch. Design rest rooms, parking lots, and ramps carefully to ensure access. Get professional assistance. At least 36 inches of level, cleared space should be provided to the side of benches for wheelchairs. Provide plenty of space at scenic overlooks for persons to watch and listen. Safety rails must be carefully located to ensure that the sight line of persons in wheelchairs is not blocked. Cassette tapes often can be used to enhance the experience of visually impaired persons. Again, you should always work closely with local groups and other potential users when designing trails for persons with physical disabilities.

Table of Contents

Horseback Riding

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• Trail Layout
  Single direction loops or multiple loops are suitable for horse trails. Provide routes with a variety of scenery and terrain. Wet areas and steep slopes pose extreme difficulties to trail maintenance and should be avoided. Keep water and motorized road crossings to a minimum. Open parade areas may be offered for riders to practice their skills.

• Trail Length
  Horseback riders travel at average speeds ranging from 4 to 8 miles per hour. Many day-use trails are designed to cover 5 to 25 miles.

• Clearing Width
  

  Light use:	8 feet (one-way traffic)
  Heavy use:	12 feet (two-way traffic)

• Clearing Height
  

  10 to 12 feet

• Tread Width
  

  Light use:	2 to 4 feet (one-way traffic)
  Heavy use:	5 to 6 feet (two-way traffic)

• Trail Surface
  Natural trail surfaces should be favored. A corduroy base covered with soil or woodchips is recommended for areas with erodible or poorly drained soils. Avoid using asphalt or concrete as both may injure horses' hooves.

• Turning Radius
  Turning radius is not critical on horseback riding trails. But, avoid sharp-angled turns or turns on steep slopes.

• Percent Grade
  Erosion problems often will develop on grades exceeding 10 percent. Switchbacks and waterbars may be necessary to traverse steep slopes. Offer resting grades (4 percent or less) of at least 500 feet in length at regular intervals.

  Desired:	0 to 10%
  Maximum:	10% (sustained) 20% (shorter than 50 yards)
  Outslope:	4% (maximum)

• Sight Distances
  Sight distances are not critical on horse trails unless horse traffic flows in both directions or hikers share the trail. In these cases, forward sight distances of 50 to 100 feet should be provided. Warn riders at least 100 to 200 feet in advance of all motorized road crossings.

• Water Crossings
  Keep water crossing to a minimum on horseback riding trails. Natural crossings and culverts should be favored over bridges. Bridges must be carefully designed to meet the needs and weight of horse travel. High, narrow bridges may scare some animals. Always obtain professional assistance when designing and locating horseback riding bridges.

  Bridges:	Must be located above the ordinary high water mark.
  	Width:	8 feet (minimum)
  	Weight capacity:	5 tons, variable depending on maintenance equipment and length of bridge
  Fords:	Horses can easily cross slow moving water less than 24 inches in depth. Favor stable streambeds with a sand and gravel base. Move large rocks downstream of the water crossing.

• Compatible Uses
  

  Winter:	Snowmobiling (if not used by horses in winter) or cross-country skiing and snowshoeing
  Summer:	Hiking if not heavily used by horses

• Incompatible Uses
  

  Bicycling

• Facilities
  Parking area with space for trailers, hitching post or tether line, campsite with corral, water

Table of Contents

Bicycling

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• Trail Layout
  Due to the potential dangers involved in bicycle passing, single direction trails should be favored. Loop or linear destination trails often are used. Many bicyclists are willing to shuttle vehicles in order to use high quality linear trails. Touring bicycle trails are expensive to construct and input from potential users is recommended. Mountain bicycle (and BMX bicycle) trails are less expensive to construct, but must be carefully located and their use monitored to protect the environment.

• Trail Length
  Trail lengths vary depending on the skills and expectations of the bicyclists. Bicyclists tend to travel at average speeds of 8 to 20 miles per hour. However, speeds can be dramatically influenced by user abilities, curves, and slopes. Most bicyclists can cover 10 to 20 miles in a single day; experienced riders can travel 50 miles or more. One mile generally is considered the minimum length for a bicycle trail; however, 1/4 mile loop trails with plenty of obstacles and challenges may be desired by BMX bicycle riders.

  Day use:

  5 to 10 miles (1/2 day) 10 to 20 miles (full day)

• Clearing Width
  

  Mountain bicycle:	6 to 8 feet
  Touring bicycle:	8 feet (one-way traffic) 10 to 14 feet (two-way traffic)

  Provide additional width on downhill sections and curves.

• Clearing Height
  

  8 to 10 feet

• Tread Width
  

  Mountain bicycle:	2 to 3 feet
  Touring bicycle:	3 to 6 feet (one-way traffic) 8 feet (two-way traffic)

• Trail Surface
  

  Mountain bicycle:	Natural surface. A professional soil scientist can help you examine the trail route for erosion-prone and impact-resistant soils.
  Touring bicycle:	A 2-inch thick asphalt surface with a 3- to 4-inch base of compacted gravel is recommended. Limestone fines and other crushed granular stone (3/8 inch or less) surfaces also are acceptable.

• Turning Radius
  Wide, gentle curves with good forward sight distances are ideal for bicycle travel. Never locate turns on downhill sections or at the base of a hill. Tight turns require installation of runouts and warning signs.

  Mountain bicycle:	4 feet (minimum) 8 feet or more (desired)
  Touring bicycle:	Ideal minimum radius of curvature can be calculated as follows: R = (1.25 x V) + 1.5 where: R = Radius of curvature in feet V = Velocity in miles per hour For example: 14 feet is the minimum radius at 10 miles per hour. 7.75 feet is the minimum radius at 5 miles per hour.

• Percent Grade
  Trail grades less than 5 percent generally are acceptable for bicycle travel. Avoid steep downhill grades that endanger trail users and pose erosion problems from continual braking and skidding. When possible, place unavoidable steep grades on uphill climbs. Most riders will be forced to dismount and push their bikes on uphill grades exceeding 15 percent. Switchbacks with barriers and runouts may be used on steep slopes. Motorized roadway approaches should be located on level grades or gentle uphill climbs (less than 3 percent). Because of the trail surfaces used, touring bicycle and mountain bicycle trails have similar grade specifications. On mountain bicycle trails, favor grade dips and rubber water deflectors over potentially dangerous waterbars.

  Desired:	0 to 3%
  Maximum:	5 to 10% (sustained) 15% (fewer than 50 yards)
  Outslope:	2 to 4% (maximum)

• Sight Distance
  Forward sight distances of at least 100 feet are critical at motorized road and water crossings, and on trails with traffic flowing in both directions. Although curves should be carefully designed to maintain good sight distances, turns and bends tend to help reduce travel speeds.

  Desired:	100 feet
  Minimum:	50 feet

• Water Crossings
  Culverts, bridges, or boardwalks should be used to cross waterways. Always cover bridges and boardwalks with smooth planking oriented at a 45- to 90-degree angle to the direction of travel. Gaps between planking oriented in the direction of travel may trap bicycle tires and endanger trail users. Bridge approaches should be straight, level, and at least 100 feet in length.

  Bridges:	Must be located above the ordinary high water mark. Bridges should have railings on both sides.
  	Width:	4 to 8 feet (one-way traffic) 10 feet (two-way traffic)
  	Weight capacity:	Variable, 5 tons or more for maintenance equipment

• Compatible Uses
  

  Winter:	Snowmobiling or cross-country skiing and snowshoeing
  Summer:	Hiking and accessibility trails for persons with disabilities on a limited basis

• Incompatible Uses
  

  Horseback riding

• Facilities
  Parking area, campsites, bicycle racks, information board, signs

Table of Contents

Cross-Country Ski Touring

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• Trail Layout
  Always favor loop trails over linear trails. Develop internal connector trails and cutoffs to allow different trail lengths and permit easy return access for tired skiers. Multiple, short loops with a single access point often are preferable to one long loop. Restrict two-way traffic to the access trail. If traffic must flow in both directions, provide a separate uphill and downhill segment on slopes exceeding 8 percent. When selecting trail routes, favor northeast-facing slopes, where snow cover remains the longest.

• Trail Length
  Cross-country skiers travel 2 to 8 miles per hour with most skiers averaging a little over 3 miles per hour. Desired experiences usually range from 2 to 4 hours with trail lengths ranging from 4 to 8 miles. When possible, provide several short loops ranging from 1/2 to 3 miles in length.

• Clearing Width
  

  Light use:	8 feet (one-way traffic)
  Heavy use:	12 to 14 feet (two-way traffic)

  At least 10 to 12 feet wide on steep uphill slopes to allow for herringbone or sidestep skiing techniques. Double the trail clearing width at trail or motorized roadway intersections. Provide even wider clearance or runouts on downhill sections.

• Clearing Height
  8 to 10 feet above expected snow depth

  Additional space where branches may sag with heavy snow, especially conifers

• Tread Width
  

  Light use:	5 to 6 feet (one-way traffic)
  Heavy use:	7 to 8 feet (two-way traffic)
  Uphill climbs:	10 to 12 feet

• Trail Surface
  Cross-country skiing trails require regular grooming to maintain a smooth surface. Grooming should begin when snow depth reaches 6 to 12 inches. Specialized equipment such as a large roller or drag with a packer pan may be built or purchased for heavily used trails. However, grooming also can be accomplished using the blade on a small tractor or the tread tracks of snowmobiles, small tractors, or off-road vehicles. The snowbase should be built from the bottom up, so regular grooming is critical after any substantial snowfall.

  On the trail surface, maintain the natural sod or establish a vegetative covering of mowed grasses or legumes. Vegetation plays a critical role in reducing erosion and catching and retaining the snow cover, especially on sloped sections. Remove rocks, logs, and other debris from the trail surface. Cut woody vegetation on the treadway flush with the ground. Avoid sandy soils on steep slopes as they are susceptible to erosion and tend not to hold the snow cover. If the trail will be used in summer, locate it on stable, well-drained soils and apply woodchips, shredded bark, or gravel in wet areas.

• Turning Radius
  Provide gradual curves that allow skiers to glide through them. Avoid sharp turns or provide additional trail width to allow skiers to snowplow and negotiate the turn. Never locate a curve on or at the base of a downhill slope. If a downhill curve is required, install warning signs at least 100 feet prior to entering the turn and provide a runout, widen the trail, or increase the turning radius. The runout length, trail width, and turning radius should increase as the slope becomes steeper.

  Desired:	100 feet
  Minimum:	50 feet

• Percent Grade
  Grade variations enhance the skier's experience, provided that slopes are not too steep. Novice skiers have trouble negotiating slopes exceeding 10 percent, while experienced skiers often can handle short slopes of 40 percent. Break steep climbs by short, level resting places or sections. Downhill runs should be straight and smooth. Wide switchbacks and gentle grade dips are acceptable methods for climbing steep slopes. End downhill slopes with straight level terrain at least as long as the slope or with a short rise in grade to allow skiers to regain control.

  Desired:	0 to 5%
  Maximum:	10% (sustained) 15 to 25% (shorter than 50 yards) 25 to 40% (shorter than 50 yards, experts only)
  Outslope:	0 to 2% (preferred)

  CROSS-COUNTRY SKI TRAIL GROOMING TIPS Groom shortly after every appreciable snowfall or period of drifting. Ideal grooming temperatures usually lie between -5 and 15 degrees Fahrenheit. Dry snow usually grooms best during the day when temperatures are warmer. Wet snow grooms best at night when temperatures are cooler. Attempt to maintain a smooth trail surface. Cut moguls (snow bumps on the trail) at or near their bases with the snow spread into a uniform layer. Higher cuts tend to create an uneven snow base density where the mogul often will redevelop. In limited snow conditions, try to set the drag so that snow can be pulled from the edges toward the center of the trail. As a rule of thumb, maintain grooming speeds of 4 to 10 miles per hour. Grooming too slow or too fast will result in poor trail conditions (e.g., washboarding, uneven snow compaction).

• Sight Distance
  Forward sight distances are not critical on cross-country ski trails except on steep downhill runs or where the trail crosses motorized roads, waterways, or other potential hazards. In these cases, level approaches (less than 5 percent grade) with forward sight distances of at least 50 feet are needed.

• Water Crossings
  Use straight, level (less than 5 percent grade) approaches that allow skiers to stop prior to crossings. Never incorporate frozen lakes or rivers into the trail design. Natural water crossings may be used on small, shallow (6 to 12 inches) streams that freeze over early in winter. Ice forms on the bottom of wet skis making further skiing difficult or impossible. Always favor culverts, bridges, and boardwalks, especially if deep water or steep banks are present. Bridge and boardwalk decks must be flush with the trail surface with narrow gaps or no gaps between decking boards to allow for snow accumulation and compaction. The weight and size of grooming equipment play a critical role in bridge design.
  

  Bridges:	Must be located above the ordinary high water mark and should have rails at least 42 inches above the snow level.
  	Width:	6 to 10 feet (bridges often become narrower as snow accumulates)
  	Weight capacity:	Variable depending on bridge length, 5 tons or more for maintenance equipment

• Compatible Uses
  

  Winter:	Snowshoeing
  Summer:	Hiking, bicycling, accessibility trails for persons with disabilities

• Incompatible Uses
  

  Snowmobiling

• Facilities
  Parking area, resting areas and benches at regular intervals, trail shelters every 8 to 12 miles, information board, signs

Table of Contents

Snowmobiling

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• Trail Layout
  Unlike other trails, snowmobiling trails should be designed to cross steep contours at right angles. Avoid hillside locations where the slope could cause a snowmobile to roll over. Two-way traffic is not recommended except on access trails. If two-way snowmobile traffic is required, provide a separate uphill and downhill section on slopes exceeding 8 percent. Avoid routes that cross or border sensitive plant or wildlife habitats. Consult your local department of natural resources forester or wildlife manager for additional information. Open areas may be provided near entrances for drivers to warm up their snowmobiles.

• Trail Length
  Snowmobile cruising speeds range from 30 to 40 miles per hour, with 50 miles per hour being the maximum. Day-use trails often are 50 to 80 miles in length. Obtaining these trail lengths often requires close coordination with other landowners, including government agencies.

• Clearing Width
  

  Light use:	12 to 14 feet (one-way traffic)
  Heavy use:	14 to 16 feet (two-way traffic)

  Double the trail clearing width at trail or motorized roadway intersections. Provide even wider clearance or runouts on downhill sections.

• Clearing Height
  

  Minimum:	8 feet above expected snow depth
  Desired:	10 to 12 feet above expected snow depth

• Tread Width
  

  Light use:	8 to 10 feet (one-way traffic)
  Heavy use:	10 to 14 feet (two-way traffic)

• Trail Surface
  Attempt to maintain a smooth, compacted snow base of 2 to 3 inches. Grooming may be required on heavily used trails. (See Cross-Country Ski Touring, Trail Surface, page 24.) On the trail base, favor a smooth, natural surface free of stumps, roots, rocks, and other projections. Crushed limestone, gravel, or corduroy may be added in wet areas. Attempt to maintain the natural sod or establish a vegetative covering of mowed grasses or legumes to reduce erosion, and to catch and retain the snow cover. Asphalt is acceptable when snowfall is sufficient.

• Turning Radius
  Curves should be as gradual as possible. Longer turning radii not only protect user safety, but also help reduce erosion and trail maintenance problems.

  Desired:	100 feet
  Minimum:	50 feet with runouts of 15 feet on the outside of the curve; warning signs and longer runouts for tighter curves

• Percent Grade
  Snowmobiling trails should cross contours at right angles. Select routes with grades less than 25 percent. Steeper grades are possible if the approach or runout are at least as long as the length of the slope itself. Small dips, natural waterbars, or rubber water deflectors may be used to reduce erosion. Always attempt to maintain vegetation on steep slopes.

  Desired:	10 to 25%
  Maximum:	25% (sustained) 40% (shorter than 50 yards)
  Outslope:	0 to 2%

• Sight Distance
  Sight distance varies with the maximum speed of the trail user. Post warning signs at least 100 feet prior to any potential hazards, including motorized roadway crossings, trail intersections, and steep drop-offs. Double the trail clearing width at a distance of 20 to 30 feet prior to the hazard.

  Desired:	100 feet or more
  Minimum:	50 feet

• Water Crossings
  Never route snowmobile trails over frozen lakes, rivers, or streams. When water crossings are necessary, culverts, boardwalks, or bridges may be used. Approaches should be smooth and level (0 to 5 percent) with forward sight distances of at least 100 feet. Bridge and boardwalk decks must be flush with the trail surface with narrow or no gaps between decking boards to allow for snow accumulation and compaction.

  Bridges:	Must be placed above the ordinary high water mark.
  	Width:	8 feet (minimum) 10 feet (desired)
  	Weight capacity:	5 tons or more depending on size of maintenance equipment

• Compatible Uses
  

  Winter:	None
  Summer:	Horseback riding, hiking, or bicycling

• Incompatible Uses
  

  Cross-country skiing, snowshoeing

• Facilities
  Parking area for vehicles with trailers, shelters or rest stops on trails longer than 15 miles, rest rooms, information board, signs

Table of Contents

References

References

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