The Pilatusbahn—the steepest rack railway in the world—has operated successfully since its opening in 1889 over a route of 4.62 kilometers (2.87 miles) between Alpnachstad on Lake Lucerne and Pilatus Kulm, rising 6,791 feet (2,070 meters) above sea level. This results in a gradient of 48%, or a rise of nearly one meter in two meters of run on the steepest sections of the line, which amounts to about a quarter of its length.

To keep the propulsion cogwheels from literally climbing out of their mating racks on the steepest portions of the Pilatusbahn, Zürich engineer Eduard Locher (1840 - 1910) devised a unique system that turned the rack on its side. The rack actually was doubled, engaged by opposing twin horizontal cogwheels. The combination not only ensured positive meshing of the racks and wheels even under extremes of loading, but guided the cars along the rails in place of conventional flanged running wheels and literally locked the cars to the mountainside.

Locher's concept uses a narrow gauge (31.5 inch or 0.8 m) that allows sharp curves and lightweight rolling stock. All the car components, including engine, boiler, and passenger compartment, as well as water tank and coal bins, were mounted on one four-wheel chassis. The original 32-passenger steam cars averaged 2 to 3 miles per hour (3 to 4 kilometers per hour) and took over an hour to reach the summit. See ASME website for more information