Railroad tracks, unlike roller coaster tracks, have much gentler grades. On most railways, the steepest grades are 1 in 40 (a grade of 2.5%). Roads, on the other hand, can have grades as steep as 1 in 6. One way in which railways have been able to attain elevation on a mountainside is by using a zigzag, or switchback, design. In the late 1860s such a railway – the Zig Zag Railway – was built in the Blue Mountains of Australia. Ten years later, the Darjeeling Himala yan Railway climbed the southern part of the Himalayas in India. In the United States, logging railroads often used this design to overcome high grades.