Zig zag (railway)

While this may be required purely from an operations standpoint, it is also ideal for climbing steep gradients with minimal need for tunnels and heavy earthworks.

[2] Some switchbacks do not come in pairs, and the train may then need to travel backwards for a considerable distance.

[4] Zig zags tend to be cheaper to construct because the grades required are discontinuous.

Civil engineers can generally find a series of shorter segments going back and forth up the side of a hill more easily and with less grading than they can a continuous grade, which must contend with the larger scale geography of the hills to be surmounted.

Zig zags suffer from a number of limitations: If the wagons in a freight train are marshaled poorly, with a light vehicle located between heavier ones (particularly with buffer couplings), the move on the middle road of a zig zag can cause derailment of the light wagon.