switchback

A switchback is a type of route on a steep slope that changes direction with abrupt turns to gain or lose elevation. By alternating back and forth, a switchback reduces the grade of a climb compared with a straight ascent and can be found in roads, railways, and hiking trails. The term often describes hairpin turn sequences on a mountain road, but the concept applies to any path that reverses direction to ascend.

In road construction, switchbacks consist of a series of hairpin bends connected by short level stretches. Drivers and vehicles must navigate near-straight segments, tight radii, and oncoming traffic in some designs. Switchbacks allow access on steep terrain where a direct ramp would be impractical, though they increase travel distance and can require guardrails, road signs, and seasonal maintenance.

Railways and funicular systems use switchbacks to gain altitude when gradients exceed the practical limit for straight climbs. A locomotive may traverse a series of reverse-direction sections, sometimes with a summit station or passing loops, before continuing upward. Some mountain railways employ cog wheels or racks to negotiate the gradient along a switchback sequence.

Hiking and mountain trails use switchbacks to reduce erosion risk and to moderate the slope. Switchback trails are common in national parks and alpine regions, making steep terrain walkable and safer by spreading the grade over a longer distance.

See also: hairpin turn, serpentine, zigzag path, zigzag railway.