Quote:
Originally Posted by Fritzdude
Light weight would be pivotal. I'm sure that levitating a 1000 lb capsule is probably easier than levitating a 55,000 lb train.
The intriguing aspects are that issues with ROW, which are huge, are nearly solved with this idea. Instead of using eminent domain to vacate people's property, you simply pay them an easement to put a 4 ft diameter pole in their yard.
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It's not that simple, though. If they are as low impact as they say, fine, but you could elevate a light rail too, Honolulu is doing an elevated line now. You still have ground conflicts, though. And I have not seen anything that tells me why this elevated structure is inherently cheaper than any other elevated structure. It still have to hold all of its mechanical equipment, power, the pods, etc.
Doing some math (somebody check it please). They claim the capacity of a 6-lane highway (I'll assume that means 3/3). So uni-directional capacity of, say, 4,500 per hour. That's the same as light rail at crush load, using 3-car consists, at 6 minute headways (or slightly more, if you're assuming much higher than 1 person per car, but let's run with these numbers for now - 6-minute LRT headways). And let's assume 2-people per pod. Yes, even if they can hold 4, if it's on-demand travel, it's a carpool model, and most pods aren't going to be at capacity, or else you slow down per-hour movements waiting for a pod to fill. 2 is probably too high, actually. But you'd need ~2,250 pods each direction per hour to match light rail.
So we can't compare the 55,000 pound train to a 1,000 lb. pod. We have to compare it to 225x 1,000 lb. pods. And it's more like 109,000 pounds full, times 3 for a 3-car consist. So 225,000 pounds PRT versus 327,000 pounds LRT, for the same uni-directional operating capacity. That's hardly an advantage, and that's assuming the pods are actually 1,000 pounds, which seems quite light. The math is definitely fuzzy, though - either it's very light, or it has good capacity... you can't have highway capacities, on-demand travel, and run a small number of pods. Something has to give there, my guess is, it would take a lot of pods. The 1973 plan had 800 in the whole system, but never claimed to have on-demand anything. Basically, those were miniature elevated buses.
Claims of 12,000 pods per hour are absurd (compared to 1,500 cars per lane per hour). The best automated traffic systems aren't projected to come close to that. I think that's somebody's back of the napkin calc. But you're still going to need some safety margin, passing "lanes" (unless nobody's going to get on/off of these things), and you're not going to achieve ingress/egress of those vehicles assuming 18 second headways. You can use high-technology all you want, people are still human beings, and somebody is going to stumble getting on, and it isn't going to line up perfectly with your 18-second opening, and viola, your capacity is cut in half. Or you "double track" it, but then it's not such a low-impact footprint anymore. So half that 12,000 is a much more realistic number. Which is fine. But it makes the whole concept look shoddy. How
do folks get on/off, and still maintain a continuous 30-second headway flow of pods?
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