switchbacks

A switchback is a section of a road or trail that makes a sharp turn to gain elevation gradually by reversing direction at each bend. Switchbacks are common in mountainous terrain and are designed to reduce the grade that vehicles or hikers must traverse.

In road construction, switchbacks take the form of hairpin turns or tight bends that redirect the route up a slope. Their radii are limited to fit the available space, and built segments are often separated by short straight sections to provide sight distance for drivers. Proper drainage, paving, and guardrails are important for safety, especially in icy or wet conditions.

On hiking trails, switchbacks serve to lessen the steepness of the ascent or descent, preserve soil stability, and minimize erosion by distributing the slope over multiple shallow grades. They may be signed and maintained to guide hikers and prevent off-trail travel.

Variants and related terms include serpentine or zigzag alignments, spiral ramps used in rail or mining, and switchback roads in various access projects. The term switchback can also describe a reversible route in other contexts where direction is repeatedly changed to gain altitude.

Advantages of switchbacks include reduced grade and improved traction; disadvantages include longer travel distance and potential for increased maintenance and danger from sharp turns. They are planned with attention to sight distance, gradient, and environmental impact to balance navigability with safety.