Trolleys are reappearing in cities such as Portland, Ore., Dallas, Memphis, Tenn., and Charlotte, N.E.

Electric trolleys were introduced in the late 1800s and signaled a new mobility for working-class people formerly confined to their neighborhoods. By 1917, there were nearly 45,000 miles of tracks nationwide.

San Francisco's 17 cars were designed in the 1930s at the request of presidents of electric car companies in the United States and Canada who wanted standardized, improved and streamlined street cars. They got cars that were among the sturdiest and most reliable transit vehicles ever made.

Trolleys Were Thought to Have Faded

Then, with the beginning of gasoline-powered buses and underground subways, most cities gradually stopped using trolleys. They still operate in Boston, Newark, N.J., and Toronto.

But only in New Orleans and San Francisco are trolleys a major transportation mode. In New Orleans, the 14.5-mile St. Charles line has been running since 1835 and remains one of the city's busiest transit routes. San Francisco rescued several rusting cars for its 3.5-mile F-line, which began service in 1995 and accommodates about 7,600 riders each day.

Now, the 50-year-old trolley cars move up and down Market Street, the main commercial artery of the city, and link the bus terminal, the Financial District and the Castro district, the heart of the city's gay community.

So far, the sleek, steel-wheeled cars, which draw 600 volts of electricity from overhead wires through antenna-like poles, have performed well. Like the cable cars which are pulled up and down hills by a wire rope under the street, the trolleys also require grooved tracks.

For San Francisco, embracing vintage trolleys also has proven to be smart public policy. The city recently imported nine street cars from Italy for about $32,000 each. A new car costs more that $2 million.