The evidence indicates that the air brake and the manual brake were quickly applied by the brakeman of cab #1, but that in the current configuration, the brakes do not have sufficient capacity to stop the cabins in motion without their empty masses being mutually balanced by the connecting cable. There- fore, the existing brakes does not constitute a redundant system in case of a failure in the connecting cable.

So the braking system is insufficient to stop after a broken cable.

There's more than a wheel brake system. There's a mechanism to clamp against the track slot from both top and bottom. See Fig. 2, right. Apparently it wasn't enough.

Funiculars are a problem because they're too steep for railroad wheel brakes, too heavy for elevator braking systems, and rare enough that there are not good standards for them. Angels Flight in LA has had two major accidents, one in 2001 and one in 2013.[1][2] Different causes. The 2001 accident was due to bad design - only one cable, no track brakes, and a system where each car had its own winding drum. The spline connecting the drums failed. The 2013 accident, after a total redesign and replacement of the hauling system, was due to bad maintenance. So bad that it involved a stick being used to hold down an override switch.

Elevator rail brakes are often jam brakes - once they're triggered, a wedge is jammed between brake and rail such that motion forces it into tighter contact. Stops with jam brakes are rather drastic. San Francisco cable cars have a jam brake for emergencies. That's the red lever, which drives a wedge into the slot. When used, there are usually passenger injuries and the wedge will be welded to the track by frictional heating.[3] So that's for serious emergencies only.

[1] https://www.ntsb.gov/investigations/AccidentReports/Reports/...

[2] https://www.ntsb.gov/investigations/AccidentReports/Reports/...

[3] https://www.cbsnews.com/sanfrancisco/news/cable-car-6-riders...

It's my understanding that this particular funicular system uses eight shoe brakes, where rubber pads basically clamp a metal track (from above and below) causing friction.

Hearing some local experts, they often mention that this is physically not enough to stop a 14 ton vehicle (plus passengers) going downhill when the slope is as high as 18%. So basically even if in perfectly working condition, the bake pads or wheels would just slide down the tracks as there's not enough friction for the resulting force.

Maybe something like a rack and pinion railway or some other kind of drastic metal locking mechanism are the only realistic way to prevent catastrophic events when the cable breaks/detaches, considering the masses and slopes involved here?