A Moving Landmark

San Francisco has the last manually operated cable car system in the world with three lines operating on those steep hills.   The cable cars got their start when a heavily laden horse drawn streetcar slipped backwards on a slippery street causing the animals to die. A witness, Andrew Halide used wire rope (the same that was used for the bridges) to start the first cable car system in 1873.  Eventually there were 23 lines, but with electricity available there was a push to convert lines to electric lines and after the 1906 quake this escalated leaving just a few lines.  In 1947 there was a push to eliminate them altogether in favor of buses, but the public fought for them to be retained.  In more recent years the systems were completely replaced and now they are one of the most popular attractions in the city and one of two moving National Historic Landmarks.

The technology behind them is simple.  There is an underground cable that runs under the trolley.  The cable is gripped with a vise-like mechanism that is operated via the grip lever in the front of the car and then the cable pulls the trolley along.  There are three brakes for when they want to stop.  The drawing shows the extent of the infrastructure underneath the cable car line.  The system is described in this 1881 article

At one of the intersections, two cable lines intersect. Because the California Street cable crosses above the Powell cable, the Powell cable must be dropped lest it slice the California cable in half, and the cable car must coast across the intersection. The cable car gripman must “drop the rope” precisely as the Powell car crests the hill, or the car will lose its momentum and slide backwards to Pine Street. It’s probably the trickiest maneuver a grip has to execute on the system.

Click the link and take a ride down the hill.