A straight road going straight up a mountain would be far too steep for cars, trucks, or bicycles to climb. Zigzagging and curving lengthens the distance, making the overall slope (or gradient) much gentler and safer to handle. Furthermore, when driving downwards, driving straight down a very steep mountain causes vehicles to pick up too much speed, so the curves and switchbacks in the road oblige drivers to slow down and give brakes time to cool. And that is why we have such bendy roads in the Swiss Alps as pictured here!