By 1960, they were found in only a few cities such as Boston, Philadelphia, and San Francisco. It is popularly believed that a conspiracy of auto and oil companies killed the streetcars. In fact, buses have several major advantages over streetcars. Their routes are far more flexible, since they can be altered with a turn of a steering wheel, while rail routes can only be changed with expensive and time-consuming construction. Since buses carry their own fuel, they don't require maintenance of overhead wires to transmit power.
Buses are much less sensitive to breakdowns.
When a streetcar breaks down, every other car on that track is delayed. When a bus breaks down, it can quickly be replaced and no other bus is delayed. Despite the streetcars' disadvantages, transit advocates today are promoting light rail in many American cities. Close to a dozen cities have opened new rail transit lines in the past decade, and many more are considering such lines. Yet the experience of new light rail lines is that they cost far more and carry far fewer riders than anticipated.