19
Aug

2013

Marginal Station vs. Marginal Length Cost

Post by Steven Dale

(Note: It’s been a while since I’ve posted on The Gondola Project. It’s been a busy summer with lots of changes to our company and our site. We’ll let you all know about the details in the coming months, but in the meantime, I’d like to extend a big thanks to Nick and Charlotte for holding down the fort while I’ve been awol.)

One of the problems the cable industry faces (like most transit industries), is prospective customers who fear nuance. Prospects often don’t care about the complexity of a system, they simply want to know how much it costs “per kilometre” (or “per mile” for our American friends).

Here’s the problem: It is virtually impossible to provide a per kilometre cost for a cable transit system. In fact, it’s virtually impossible to provide a per kilometre cost for any transit system, period. It’s kind of like that old idiom—how long is a piece of string?

No where does this become more obvious than with the relationship between the length of a cable transit line and  the number of stations within a cable transit line.

Let’s assume, for example, a given 1 kilometre long cable transit system that has two stations and costs $8mm. Let’s call it Line A.

Now let’s assume a second cable transit system. This one is the same length of Line A (1 kilometre) but has a total of three stations rather than two with all else equal. Let’s call this system Line B.

Now, let’s assume a final third cable transit system. This one has only two stations but is double the length of Line A—it’s 2 kilometres long with all else equal. Let’s call this system Line C.

Okay? Got it? No? Let’s review then:

  • Line A: 1 km, 2 stations.
  • Line B: 1 km, 3 stations.
  • Line C: 2 km, 2 stations.

Which line is more expensive? Line B or Line C?

People who imagine the problem as a question of cost-per-kilometre will invariably say Line C is more expensive than Line B because Line C  is double the length of Line B.

Problem is, they’d be completely, 100% wrong.

In cable, the marginal cost of stations is almost always more expensive than the marginal cost of length.

People considering a cable transit system of their own need to understand that. Per-kilometre costs estimates are blunt tools that don’t tell you what you really want to know—and they often lead to early-stage financial estimates that tell a completely false story.

 



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Comments

  1. Matt the Engineer
    Yes. Gondolas are more like airports than highways. With airports you pay for the stations and the rest is free. Cable is pretty cheap on the grand scale, so I'd guess for a typical medium to large city in the US or Canada cost would be (in order of magnitude): Price of land (for stations, towers, air rights) Cost of station infrastructure (stairs, elevators, foundation, restrooms...) Cost of station equipment (motors, pulleys, etc.) Cost of towers Cost of gondola cabins Cost of cable Most of these scale on the number of stations. The only ones that scale by length are the cable, towers, and some portion of the land cost. The largest numbers (if my guess is correct) make everything else difficult to compare between cities. Cost of land is vastly different in NYC compared to Caracas. The cost of construction is vastly different in North American cities compared to South American cities (due to the cost of labor and construction standards). And the cost of land is also variable based on local laws (for example: can I buy air rights or do I need to buy the whole property?). The closest I'd think you could come up with as a first cost estimation would be $/(station * real estate factor * labor cost factor). These wouldn't be too tough to calculate, but wouldn't be perfect and certainly wouldn't be easy to communicate to groups like politicians.
  2. Matt the Engineer
    (I'd love it if you could keep paragraph structure in the comments!)
  3. Matt the Engineer
    (trying again. sorry about the clutter) Yes. Gondolas are more like airports than highways. With airports you pay for the stations and the rest is free. Cable is pretty cheap on the grand scale, so I'd guess for a typical medium to large city in the US or Canada cost would be (in order of magnitude): Price of land (for stations, towers, air rights) Cost of station infrastructure (stairs, elevators, foundation, restrooms...) Cost of station equipment (motors, pulleys, etc.) Cost of towers Cost of gondola cabins Cost of cable Most of these scale on the number of stations. The only ones that scale by length are the cable, towers, and some portion of the land cost. The largest numbers (if my guess is correct) make everything else difficult to compare between cities. Cost of land is vastly different in NYC compared to Caracas. The cost of construction is vastly different in North American cities compared to South American cities (due to the cost of labor and construction standards). And the cost of land is also variable based on local laws (for example: can I buy air rights or do I need to buy the whole property?). The closest I'd think you could come up with as a first cost estimation would be $/(station * real estate factor * labor cost factor). These wouldn't be too tough to calculate, but wouldn't be perfect and certainly wouldn't be easy to communicate to groups like politicians.
  4. Matt the Engineer
    (I give up)
  5. Station cost vary with technology. Detachable systems like gondolas (MGD,BGD,TGD) need large stations with a accelerating mechanism. So stations are very expensive. If we use vehicles which are fixed to teh cable the staions can be buolt much smaller. Funiculars and Aerial Tramways need only a station that is as long each vehicle. For example Seilbahn Rigiblick in Zürich is only 385m long but has 5 stations. There is a constraint that station must be placed symmetrically to the middle of the line, but in some cases it is achievable. Theoretically pulsed gondolas would be the most cost effective solution if stations are even spaced. another thing is taht we cannot built cables with unlimited length. There is a technical limit for cable length and that is if teh cable is so heavy that it cannot pull its own weight. So we must place a station at least every less tan five kilometers. Which means we have to use detachable vehicles to provide a continuous ride. For this reasons cable transit should be relatively short and only have a few stations.
  6. Thats also the same situation for subways/metro , where the cost of stations could be a very significant part of the total cost; but this doesn't seem to be an obstacle.