I went to the Cable Car Museum, and... it's both ingenious and crazy to have the vehicles have neither engines nor power, and have the street full of machines instead. They just get pulled along, and let go of the moving cable when they need to stay still.
Sure, roller coasters are like this, and so-called smart-highways really should be... The museum has lots of giant wheels rotating cables, and the genius/madness of it is all impressive.
There's also a great exhibit about how the City tried to replace these with buses that couldn't even climb the hills back in the 40s, and how citizens organized to prevent that madness, in favor of keeping this effective-on-hills-and-wild madness that we like better. Yaaay, people!