San Francisco's cable cars are a type of tram or streetcar. That is, they are a form of public transport running on rails through the streets. What makes the cable cars unique is their method of propulsion - the cars themselves have no form of motive power. In a slot in the ground between the tracks there is a cable which is moving all the time. A mechanism on the car reaches down into the slot and grabs on, pulling the cable car along. The cable itself is driven from a central powerhouse.

Cable cars have operated in a number of cities around the world, mainly in the United States, but San Francisco is the only place where they are still running, and they are seen as a part of the city's heritage.

Each cable car is driven by a 'gripman', who operates the levers that drive the car. The gripman also has the task of ringing the bell to warn traffic and pedestrians in front to get out of the way. The sound of the cable car's bell is one of the distinctive sounds of San Francisco.

History

The city of San Franciso has a design flaw - it is built on a series of steep hills. In other countries, this would be overcome by building roads that followed the contours of the hills - not so in America, where roads are so often aligned with compass directions. In most of the centre of the old city, roads go either North-South or East-West. As a result, many of the streets in San Franciso are very steep. In the 19th Century, in the days of horse-drawn vehicles, this posed a serious problem. Horses were unable to pull carriages up some of the steeper streets.

The cable car was invented by Andrew Smith Hallidie. Born in England, he moved to America in 1852 and found many uses there for a new type of steel cable which had been patented by his father. In 1869 he witnessed a horrific accident in San Francisco: a heavily loaded carriage pulled by five horses slipped backwards, killing the horses. He started to think about a way of pulling the carriages mechanically, and of course his thoughts turned to steel cable. By 1873 he had designed and built the first cable car. It ran along Clay Street.

By the 1890s, there was an extensive cable car system in place with many different lines run by different companies. There was also a competing system of trams run by overhead electric wires. A major blow to the cable car system was the earthquake in 1906. In the subsequent fire, most of the city was burnt down, and the cable system was damaged. Electric trams were quicker to repair than the cable cars, so some of the routes were converted to trams.

By 1947 the city was considering scrapping the cable cars completely and replacing them with buses. This led to a woman called Friedel Klusssman setting up the Citizens' Committee to Save the Cable Cars, which lobbied for their retention. The campaign was successful and three lines were retained. The running costs are high, but it is now acknowledged that the cable cars are an intrinsic part of San Francisco and a draw for the tourists.

In 1982, the entire system was overhauled, necessitating a closing of all lines for two years. New tracks were laid on much of the routes, many cars were rebuilt and the powerhouse was almost completely rebuilt. The newly-refurbished system was opened in June, 1984 and has been running ever since.

The Modern Cable Car Lines

There are now only three cable car lines left in San Francisco. Two of the lines run basically north/south, and join together around Washington Street, running south from there along the same route as far as Market Street. The third line runs east/west along California Street.

Powell-Hyde and Powell-Mason

These two lines both start at the southern end of Powell Street, almost at Market Street. They share the track from there as far as Jackson Street, where the two lines split. The Powell-Hyde line goes west as far as Hyde Street, climbs over Russian Hill and down to the bay at the north end of the city at the Victorian Park. The Powell-Mason line also goes west for a short distance but then turns north along Mason Street, along Columbus Avenue and then along Taylor Street, ending up at the junction of Taylor and Bay Street, a few hundred yards' walk from Fisherman's Wharf.

The two lines use identical cars; each car can operate on either line - the wooden sign along the roof giving the name of the line can be flipped over by a lever to show the name of the relevant line.

The cars are divided into two sections. In the front half, the gripman occupies the centre of the car. There is a row of seats on either side, facing outward, with their backs to the gripman's levers. Outside these are running boards where passengers can stand and hang on to the many bars. The back half of the car has an enclosed section with seats facing inward. At the very back is a small platform where the conductor stands.

Since these cars have a front and a back, they must be turned at the end of the line, so there is a turntable capable of taking the car. This is manually operated, literally by three men pushing the car around. The turntable at the junction of Market and Powell Streets marks the beginning of two lines and is the busiest spot in the whole system.

California Street

The California Street line runs along just the one street, with no bends. These cars are different, with a central enclosed part, and grippers at both ends. This means that the cars don't need to be turned at the ends of the track and there are no turntables.

Travelling on a Cable Car

Before you get on a car, you must buy a ticket. The tickets are expensive for a single journey but good value for a day pass. If you're going to be hanging around the city, it's best to buy a day pass, as you can hop on and off the cable cars for just a couple of blocks, to get up a steep hill. Once on the car, you'll need to show your ticket to the gripman or the conductor.

Next you must consider where to get onto the cable car. The terminus might seem like the obvious choice, but you'll have to join a queue, and you might be waiting an hour at busy times. If you're prepared to stand on the running board, you can join the car a couple of blocks from the terminus. Even though the car is filled at the terminus, they usually leave space for a few extra people to get on later.

You can only get onto a cable car at designated stops, which are marked by signs at the side of the street. Remember, while you stand and wait at the kerb, you must walk out into the street to get on the car; it won't pull in to the side to meet you. You can normally only leave a car at a stop as well: you let the gripman or the conductor know you want off at the next stop. Don't pull the conductor's cord - this is for the conductor to communicate with the gripman only. If you're on the running board, you can hop off when the car is stopped at traffic lights.

The Job of the Gripman

If you're on the running board, or in the outward-facing seats, you've a chance to see the gripman at work. It's a strenuous activity pulling those levers - there's no power assist. There are three levers:

• The first is the gripper. The cable is moving continually under the car at a speed of 9.5 miles per hour. The gripper must be slowly applied so that the car moves smoothly from rest up to that speed. When it is going full speed, the gripper is locked onto the cable. But not for long - it must be released in lots of different situations: going down a hill, going round a corner (where the cable is supported by a wheel), and when stopping.

• The brake lever is used to stop the car, and also to keep it going at a constant speed when going downhill.

• The third lever is one that you should never see in operation. Painted red, it is the emergency brake. It works by sticking a spike into the track - it does quite a lot of damage when operated, but emergencies are emergencies.

The gripman also rings the bell to warn traffic and pedestrians ahead. Gripmen are very proud of their bell-ringing; each has his own patterns, and there are bell-ringing competitions.

The Cable Car Museum

All three lines are driven from the giant powerhouse in the Cable Car Museum at the junction of Mason and Washington Streets. Admission to the museum is free. The main thing to see is the working cable-driving machinery, which is running all the time, powering four cables. Originally this would have been driven by a steam engine but now it is electrically powered.

Each cable comes into the building underground and is sent around giant pulley wheels known as sheaves, which feed it to the cable-tensioning system before going around the cable drive wheel, after which it is fed back out to the street. The cable itself is 15/16 inch thick (23.8mm) and is made from steel fibres woven around a rope core to give it flexibility.

One of the four cables serves the California line. One serves the shared section of the Powell-Hyde and Powell-Mason lines from the museum south to the terminus. The other two run the independent sections of the Powell-Hyde and Powell-Mason lines.

The museum also contains an exhibition of the history of the cable car system. You can see examples of the different types of car used over the years, including one from the very first line, in Clay Street.