Why do some mountain roads have so many hairpin bends?

Mountain roads must balance steep topography, drainage, and vehicle safety. If a road went straight up a slope, the gradient would often be too steep for cars and trucks to handle, especially in snow or ice. Switchbacks lengthen the route so the incline is gentler. They also reduce the chance of vehicles losing traction and allow engineers to follow stable ground instead of cliffs or loose scree. Famous mountain passes in the Alps, Andes, and Himalayas use these bends to climb safely.