Independence vs. Interdepence

Post by Steven Dale

I’ve heard the argument that cable’s not a viable form of transit because vehicles cannot move independently of each other. Standard transit technologies – the argument goes – are self-propelled and are therefore immune to problems experienced by other transit vehicles on a line.

This argument is only half-true. The first part is true: Yes, in standard configurations all vehicles are self-propelled. The second part is false: Just because all vehicles move independently of one another, does not mean they are not impacted by each other.

Consider, for example, how many times a fully-functioning streetcar, LRV or subway is stuck in place due to the malfunction of a vehicle ahead of it. Because all vehicles share the same right-of-way, they are just as interdependent upon each others’ movement as a cable system. Even PRT would be susceptible to this (if it existed), and independence is one of that technology’s key selling points.

A problem in one part of a transit system will always reverberate throughout the rest of that system, independent or not.

Buses, one could argue, avoid this problem entirely, but their full independence means high operational costs due to the need for a large number of drivers. (Their independence, however, is also questionable due to the mitigating impacts of traffic, stop lights and scheduling.)

The independence argument is a red herring and completely masks three significant advantages to interdependent movement:

  1. Cheap Automation – As cable systems move interdependently, automation can be accomplished easier and more cost-effectively than complex automation of independent vehicles. You don’t need a driver in each vehicle – human or otherwise.
  2. Economies of Scale – Rather than build 30 engines to propel 30 vehicles, cable systems build one engine to move 30 vehicles. The economies of scale that occur here are one of the single greatest reasons for cable’s cost-effectiveness.
  3. Reliable Headways – Ever waited for half an hour for a bus or streetcar only to have four arrive at one time? That’s what happens with independent vehicles. In a cable system, that doesn’t occur. Because vehicles move interdependently, chain-gangs of vehicles (‘bunching’ as it’s called) is a virtual impossibility.

It’s easy to get caught up in terms like “independence” because it sounds like a good thing. But – really and truly -independence is a non-argument.

After all, independence without impact is irrelevant.

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Want more? Purchase Cable Car Confidential: The Essential Guide to Cable Cars, Urban Gondolas & Cable Propelled Transit and start learning about the world's fastest growing transportation technologies.


  1. An important point is that a gondola actually has three motors: Main Drive: which is electric powered and can power the system at full nominal power Auxillary Drive: Electric drive either same as main drive or at a lower rating used when main drive has a failure or is under maintenance Emergency drive: Diesel Motor comes into use when main and auxiliary motor fail can propel all vehicles to the next station. Therefore it is very unlikely that a CPT will be forced to stop. Of course the single point of failure is the cable but with a well maintained and designed system they should be not much issues. Splitting up the CPT in section with different cables will further minimize the impact of a single fault.
  2. Cheap automation. Reliable headway. People don't understand that gondola technology, because it is mostly used to move people from A to B (bottom of ski hill to top of ski hill) is, for the most part, still back in the 19th century. The first trains ran between two stations: A and B. When the line was extended to C, the train stopped at B, then continued. Then some smart guy figured out how to shunt the train into a siding using a simple mechanical switch. Sometimes the siding was a station or 'yard' or sometimes out in the boonies to a 'high ball' jump the queue and roar on through. Except for automating the switch, that's essentially were all rail-based technology still stands - or, if you're a passenger service dependent upon someone else letting you borrow their track like Via (Canada) or Amtrak (US), sits. Pun intended. It's interesting that 'back when', choochoos used roundhouses to rotate the engine so that it always not only 'looked' right, it 'worked' right (they later broke it into two sections, forward and rear), while now, when you check out a typical 'modern' commuter rail service - like, say, Ontario's 'GO Train' - half the time it's running backwards. Funniest damn contraption you ever saw. Which is why I call the 'Front Runner', northern Utah's multi-billion dollar cab and cadoodle, 'Rear Runner'. I can hear it now, Supervisor to Engineer: "If you're going to ram something big, try to do it with the 'hard end'. But as demonstrated by Medellin and others, gondola 'art' has, with detachability, mid-stations, directionability, and other, not only caught up to rail - but because once you've detached a cabin you don't have re-attach it to the same cable, your simple switch/rail arrangement can attach it to any number of cables or, for that matter, to any other complimentary guideway – it's leap-frogged it. Literally (check out the giant ferris wheel at St. Anton's Galzighaln. I'd love to see a cartoonist's depiction of a Red Rocket on a ferris wheel). On a simpler and less-expensive plane, they do somewhat the same at places like Snow Basin, a ski resort just over the hill from my home where, at the flip of a switch, cabins are shunted onto a sloped cog-conveyor that drops them down into an underground parking/maintenance garage. There is no reason why the same simple-cheap technology could not, for instance, switch cabins to another line running thataway or, in a station, move them to the side (or, like Galzighaln, up or down) to permit an express cabin to 'roar' on through. Speaking of economies of scale, since they're are already there (and assuming that visibility is not an issue), think about the possibility of suspending two (or, holy gondola, more) ropes from the same tower - the top tier non-stop (for sight-seeing or 'express'), the lower (commuter) stopping at each station. The stations servicing the express line are 'bi level'. Stay tuned... Side note. There's not a train or a bus in the world these days that doesn't have heat or AC. Outsiders would find it quite unbelievable that, for all gondolas can do, except for seat warmers quick-charged within stations, the art has neither heat nor AC. No prob in the cold where most riders are bundled up for skiing, but if we're seriously contemplating moving our product into the 21st century (or running it at night - especially during winter with short daytime) we're going to have to address the issue. Stay tuned on that as well. Bruff
  3. Bruff, As per my understanding, heating and AC is not a problem currently. Solar panels and rechargeable battery systems allow for those features.
  4. All great points, Matthias.

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