It's an old idea, dating back to the 1500s, but the basic concept of the funicular has remained viable over the centuries. Sometimes referred to as an inclined railway, the funicular consists of a track, a pulley, and an engine. The engine powers the pulley, which slowly draws the car up the side of a steep incline. The track is there to guide the wheels.
All of this sounds quite logical -- but what about the trip down? Wouldn't the gravitational force of a heavy rail-type car quickly tear the engine and pulley apart, flinging the passengers to their death?
It probably would, except that the original inventors of the funicular figured out that if cars were ascending and descending simultaneously, an equal number on each side of the pulley, the force of gravity would cancel itself out. The ascending car or cars serve as a brake on the others; those heading down help supply the pulling power to yank the ascending cars upward.
This is a simple concept, but not easy to put into practice. The cable must work in a continuous loop, the timing must be perfect, and there must be room for the ascending and descending cars to pass each other en route.
An example of what can go wrong was a fatal accident on the Angel's Flight Funicular in Los Angeles on 1 Feb 2001. This was an operation with four cars, two on each side of the line. For reasons still unexplained, the cable somehow escaped from its groove inside the pulley and created a loop of slack. This caused the topmost car on one line to slide backward into the car below, killing one passenger and injuring seven.
It soon turned out, however, that the Angel's Flight operation lacked the emergency brake generally built into funiculars -- a powerful, claw-like apparatus that latches onto the cable when a sudden increase in speed is detected by a mechanical device. The Angel's Flight funicular was put back into operation in November of 2008, its operators sadder but wiser.
Perhaps the best-known funiculars in the United States are the two "inclines" that haul passengers up the sheer face of Mount Washington in Pittsburgh. Not far away, the Johnstown Inclined Plane is capable of carrying at least one automobile as well as passengers, and the Lookout Mountain Incline Railway in Chattanooga, Tenessee operates on a scary grade of 72 percent. Others of note include funiculars in Quebec City, Budapest, and Santiago, Chile.