Special Structures (continued)

The advantages of climbing turns in appropriate terrain is that a larger radius turn (4 to 6 m, 13 to 20 ft) is relatively easy to construct. Trails that serve off-highway-vehicle traffic often use insloped, or banked, climbing turns so that riders can keep up enough speed for control (Figure 59). Climbing turns are also easier than switchbacks for packstock to negotiate. Climbing turns are usually less expensive than switchbacks because much less excavation is required, and fill is not used.

Figure 59—Climbing turns continue the climb through
the turn. They can be insloped or outsloped.

The tread at each end of the turn will be full bench construction, matching that of the approaches. As the turn reaches the fall line, the amount of material excavated will decrease. In the turn, the tread will not require excavation other than that needed to reach mineral soil.

Guide structures should be placed along the inside edge of the turn. Temptation-reducing barricades can be added if necessary. The psychologically perfect place to build climbing turns is through dense brush or dog-hair thickets of trees. Be sure to design grade dips into the approaches.

Switchbacks

Switchback turns are harder to build correctly, but retain stable tread on steeper terrain. Most switchbacks are constructed to a much lower standard than is needed. The key to successful switchback construction is making an adequate excavation, using appropriate structures to hold the fill in place, and building psychologically sound approaches.

Look for "natural" platforms when you are scouting for possible switchback locations. Use these for control points when locating the connecting tread. These will save you a lot of time later by reducing the amount of excavation and fill needed.

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