The San Francisco Municipal Railway operates the largest network of electric trolley coach routes in the United States. (In other cities, these vehicles are called "trolleybuses" or "trackless trolleys".) Trolley coaches excel at climbing steep hills, and cheap hydroelectric power is available from a city-owned reservoir and dam in the California mountains.

I rode a lot of these critters when I was in San Francisco. Unless you look up to see the trolley poles, you might mistake them for normal buses.

On Market Street, they share the same road with both regular buses and old-fashioned trolleys (streetcars), of which two things the trolleybus is sort of a combination or middle ground.

SF also has a lot of articulated buses, too. In fact I didn't know there was such a thing as either an articulated bus or a trolleybus until I went there.