Basically, there are three cable car routes in operation, and it helps to know their respective destinations. At Powell and Market streets, there is a cable car turntable which serves as the beginning stop for two lines, the Powell-Mason and Powell- Hyde lines. The Powell-Mason line begins at the Powell/ Market turntable, and the line runs from there up and over Nob Hill and down to Bay Street at Fisherman's Wharf. The Powell-Hyde line also begins at the Powell Market turntable and runs over Nob and Russian hills before ending at Aquatic Park near Ghiradelli Square. Both these lines end near Fisherman's Wharf, but at different areas, and the routes are significantly different. Paying close attention to the signs on the cable cars will help you distinguish where in Fisherman's Wharf you will find yourself.
The California Street line runs East-West from the Financial District, through Chinatown, over Nob Hill and stops at Van Ness Avenue. Since all the cars on this line have the same routes, the signs are painted directly on the car.
Safety comes first - so there are actually three separate braking mechanisms for each of these heavy cars: the main track brakes are operated by the red lever in the front of the car, the front wheel brakes are operated by the foot pedal in the front of the car, and the rear wheel brakes are operated by the crank at the back of the car.
Every cable car is pulled along it's hilly track by an underground cable. The cable is gripped with a vise-like mechanism that is operated via the grip lever in the front of the car.
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The Wikipedia entry on the "San Francisco cable car system" contains a good overview of the system's history and actuality. For example, the section on "Recent history" states:
The cable car system is principally used by tourists rather than commuters. The system serves an area of the city that is already served by a large number of buses and trolleybuses. The Powell-Mason and Powell-Hyde lines both serve only residential and tourist/shopping districts (Union Square, Chinatown, North Beach, Nob Hill, Aquatic Park and Fisherman's Wharf), with the "downtown" end of both lines a substantial distance from the Financial District. The California Street Line is used more by commuters, due to its terminus in the Financial District.
The entry also provides a more detailed description of each line's route, for example:
- The Powell-Hyde (Line 60) line runs north and steeply uphill from a terminal at Powell and Market Streets, before crossing the California Street line at the crest of the hill. Downhill from this crest it turns left and uphill again along Jackson Street (as this is one-way, cable cars in the opposite direction use the parallel Washington Street), to a crest at Hyde Street. Here it turns right and steeply downhill along Hyde Street to the Hyde and Beach terminal, which is adjacent to the waterfront at the San Francisco Maritime Museum. Man-powered turntables turn the cable cars around at the two ends. This line is used greatly by tourists and often has long lines.
- The Powell-Mason (Line 59) line shares the tracks of the Powell-Hyde line as far as Mason Street, where it crosses Washington and Jackson streets. Here the line turns right and downhill along Mason Street, briefly half left along Columbus Avenue, and then down Taylor Street to a terminal at Taylor and Bay. This terminus is near to, but two blocks back from, the waterfront at Fisherman's Wharf. There are man-powered turntables at each end that turn the cars around. This line is also used greatly by tourists, but also some commuters.
Single-ended cars serve the Powell-Hyde and Powell-Mason lines. These cars have an open-sided front section, with outward-facing seats flanking the gripman and his collection of levers that actuate the grip and various brakes. The rear half of the car is enclosed, with seats facing inward and entrances at each end and the car has a small platform at the rear. These cars are 27 ft 6 in (8.6 m) long and 8 ft (2.4 m) wide and weigh 15,500 pounds (7,000 kg). They have a passenger capacity of 60, 29 of them seated. These cars must be rotated to reverse direction at each end of the line, an operation performed on turntables. Most of these cars were built or rebuilt in the 1990s at Muni's Woods Carpentry Division.
Each car is operated by a "gripman", as the driver is know. This is a highly skilled job that requires rigorous training (apparently along 30% of people pass the training program) and significant upper body strength. The gripman must "smoothly operate the grip lever to grip and release the cable, release the grip at certain points in order to coast the vehicle over crossing cables or places where the cable does not follow the tracks, and... anticipate well in advance possible collisions with other traffic." In addition, a "conductor" collects fares, generally manages the passengers, and also controls the rear brake on downhill slopes.
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San Francisco's cable cars are unique in that they are the only street railway in which the cars do not operate under their own power. Instead, the cars are propelled mechanically, by "gripping" a continuously moving steel cable which runs in a conduit underneath a slot between the rails. The cable, in turn, is kept in motion by an engine in a centrally-located powerhouse.
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Also, I spotted several great photos of a cable car cresting a hill on Powell street with the San Francisco Bay and Alcatraz in the background. It would be great if I could find a similar shot under copyleft, and in fact there is one in the Wikipedia entry. I'll post it separately with the required information about its licensing.