Comment by Animats

> there is a significant fixed overhead (from power usage and cable wear) to having the system running at all, regardless of how many cars are on it.

Each cable car trip costs Muni about US$20. They charge about $8.

I was amazed when I first found out how the grip worked. I figured they clamped pulleys around the cables and then applied brakes to the pulley system. Nah. It's brutally simple. They squeeze two soft metal plates around the cable. The cable wears a groove in the plates during starting and stopping. Those plates are replaced every 3-4 days. The cables are replaced every few months.

Plus the thousand or so pulleys under the street need regular attention. The whole system has way too many friction points, which means intensive maintenance.

The PCC streetcars were a really good design, built for efficient operation with modest maintenance. Their successor in San Francisco was built by Boeing Vertol, which totally botched it.[1] None of those cars are still around. The PCC cars roll on.

[1] https://en.wikipedia.org/wiki/US_Standard_Light_Rail_Vehicle