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bunt_q Apr 18, 2011 4:45 PM

I think their infrastructure costs are probably just bogus. They seem overly optimistic. But that's not the gist of this thing anyways.

I'm having trouble finding much on this "passive mag-lev" other than a bunch of articles talking about how great it is. What makes it work here, and not, say, with a conventional maglev train? (if there is such thing as "conventional mag-lev")

Brainpathology Apr 18, 2011 4:48 PM

They seem to repeat "ultra-light" as well. Maybe that's one of the justifications.. not sure how light ultra-light is or how they do that though.

Fritzdude Apr 18, 2011 5:24 PM

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.

It would surely have to cost less than a traditional rail, though by what factor I don't know. Their studies say 1/10 the cost. It's not unreasonable.

I don't think it's ideal for the city, but I could see this an option for the mountain corridors.

bunt_q Apr 18, 2011 5:52 PM

Quote:

Originally Posted by Fritzdude (Post 5245802)
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.

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?

Cirrus Apr 18, 2011 7:25 PM

There are at least two kinds of PRT systems that do work well: Bikesharing and taxicabs. They work because they're cheap and don't require new elevated railways over every street in the service area.

Of course, the PRT lobby hates bikesharing and generally ignores taxis.

bunt_q Apr 18, 2011 7:36 PM

Well, along similar lines, rickshaws (both auto and man powered), and even the extensive minibus systems of most developing world cities, are essentially high functioning and supremely flexible variants of PRT.

But not elevated...

EDIT: In those 'when I win powerball' moments, I've always thought that a savvy entrepreneur, who could find a good model of hybrid Indian-style auto-rickshaw, enclose it for weather, and hire good enough lawyers/linguists to bust the taxi unions grip on all things taxi-ish, could put RTD buses out of business (and end unemployment) in no time. I'd drive a rickshaw for a few extra bucks. :)

Cirrus Apr 18, 2011 7:42 PM

And they don't divert money away from transit...

wong21fr Apr 18, 2011 7:51 PM

Those PRT's capsules and stations certainly are ADA compliant....

...whoops, did I just double the cost?

Cirrus Apr 18, 2011 7:59 PM

Quote:

In those 'when I win powerball' moments, I've always thought that a savvy entrepreneur, who could find a good model of hybrid Indian-style auto-rickshaw, enclose it for weather, and hire good enough lawyers/linguists to bust the taxi unions grip on all things taxi-ish, could put RTD buses out of business (and end unemployment) in no time. I'd drive a rickshaw for a few extra bucks.
Busting the taxi lobby would be the hardest part.

I've always wondered how many more people would use bikesharing if we spent an extra grand per bike and gave them all electric motors.

Fritzdude Apr 18, 2011 8:05 PM

Quote:

Originally Posted by bunt_q (Post 5245837)
How do folks get on/off, and still maintain a continuous 30-second headway flow of pods?

I guess I'm interpreting - or at least imagining - a different scenario than you. Let's say the pods would hum along at 100 mph - but accelerating and slowing down would be done off the main guideway system so as to not interfere with the steady stream of traffic. Therefore, you're either going 100mph on the track, or you're consigned to the egress ramps as you either gain speed for entry or slow down for eventual disembarkment. Perhaps an entry ramp is 1/2 long or longer to make the necessary acceleration to transition onto the guideway. What can a human body comfortably tolerate in acceleration G-Forces?

Anyway, as the entry ramps eventually converge with the main gateway, the pods merge with the current flow of traffic just like cars would as the access the highway. However, the controls would be done automatically with software that determines the appropriate time for merging. So, a person might sit idle in the pod before acceleration occurs, based on some algorithm with data from the oncoming traffic. Without human failability, the computer would determine the correct spacing and allow for closer aligned pods, since they're all going the same speed and you don't have to worry about people not paying attention.

For an anology - UPS boxes don't bump into each other once they're on the main conveyor belt.

bunt_q Apr 18, 2011 8:14 PM

I assume that too. But now you're talking 4 guideways, especially in an urban environment with relatively close stations. I'm just not seeing what the advantage is over conventional transit technologies (it won't go 100mph, I guarantee, not with 1-mile station spacing).

For the mountains, I can't see anything that addresses whether or not the grades would be an issue (I'd assume yes, uphill takes more energy, no matter the technology, I'd be curious to see if it's been contemplated for a "passive" mag-lev). Also an issue potentially is the distance. This was conceived as an urban system, right?

Cirrus Apr 18, 2011 8:15 PM

If the main advantage is computer control, why not just start putting automatic computer control into normal cars? Bam! Same benefit at tiny fraction of the cost.

EngiNerd Apr 18, 2011 8:17 PM

Why couldn't cars be made to do the same though? Jump on the highway, computers take over and guide you along with radar based cruise control to the one in front of you? All could be GPS and radar based, would use existing infrastructure, and probably wouldn't even need to embed anything in the highway. And heck, the way the electric push is going, I wouldn't say it will be unfeasible in 30 years time to have all cars have a full electric cycle anyway.

edit: Cirrus beat me to it.

Fritzdude Apr 18, 2011 8:26 PM

Quote:

Originally Posted by EngiNerd (Post 5246057)
Why couldn't cars be made to do the same though? Jump on the highway, computers take over and guide you along with radar based cruise control to the one in front of you? All could be GPS and radar based, would use existing infrastructure, and probably wouldn't even need to embed anything in the highway. And heck, the way the electric push is going, I wouldn't say it will be unfeasible in 30 years time to have all cars have a full electric cycle anyway.

edit: Cirrus beat me to it.

What.. am I the only dreamer here? Yes - I guess you could have cars with radar that could drive themselves, but what about road construction, accidents, and the accordion effect of bumper to bumper traffic. That's where all the efficiencies are lost.

Theoretically, while everyone is stuck in traffic, if everyone decided to acclerate at the same time, then everyone would move in accordance. But, that's not feasible. However, computer controlled movements would be feasible. In this scenario, you're either going 100mph, or your not on the guideway.

My initial query was a system that was designed to get people up through the mountain corridors, not the city. I see too many problems there. But through the mountains, egress points could be spaced out every 5 -10 miles and you would only need a half mile entry ramp to get someone up to 100 mph without G-forces crushing their skull.

Yeah - you would need to be strapped in. It's sort of like a commercial roller coaster on take off. But the point is that you'd get to your destination very quickly. Isn't that half the battle?

bunt_q Apr 18, 2011 8:42 PM

The point is with computer controlled cars there wouldn't be traffic delays and accidents. It would operate exactly the same as the PRT. Lanes are guideways. It's coming, it's not even a far fetched dream anymore.

As for construction, transit suffers from that too.

Fritzdude Apr 18, 2011 8:47 PM

Quote:

Originally Posted by bunt_q (Post 5246099)
The point is with computer controlled cars there wouldn't be traffic delays and accidents. It would operate exactly the same as the PRT. Lanes are guideways. It's coming, it's not even a far fetched dream anymore.

As for construction, transit suffers from that too.

On the ground, there will always be something blocking movement, whether it be cross traffic, bad weather, pedestrians, a guy with a flat tire, or an ambulance coming through. A million things effect movement on the ground.

On the contrary, when you're 20ft up in the air, nothing gets in your way. :cool:

Cirrus Apr 18, 2011 8:50 PM

Cars are allowed to break down but PRT trams never would? The effects of bad weather end 19 feet above ground, and everything above is always clear?

Come on.

bunt_q Apr 18, 2011 8:56 PM

Quote:

Originally Posted by Fritzdude (Post 5246103)
On the ground, there will always be something blocking movement, whether it be cross traffic, bad weather, pedestrians, a guy with a flat tire, or an ambulance coming through. A million things effect movement on the ground.

On the contrary, when you're 20ft up in the air, nothing gets in your way. :cool:

Except the maintenance man working on the thing that's holding you up there. Wheee. Ice, pigeons, and all of the wires, poles, etc that will have to be relocated first so that nothing interferes (not included in the easy cost estimates, of course).

Of course, none of those things interfere with a conventional train once you elevate it, too. This entire plan depends on grade separation that is magically cheaper than any other grade separation on earth.

Fritzdude Apr 18, 2011 8:59 PM

Quote:

Originally Posted by Cirrus (Post 5246106)
Cars are allowed to break down but PRT trams never would? The effects of bad weather end 19 feet above ground, and everything above is always clear?

Come on.

I guess when we get a massive blizzard, it would probably be prudent to stop the PRT system, but those are the anomolies. You can manage exceptions. However, you can take comfort that at least you won't have to worry about a moose walking out in front of you.

Brainpathology Apr 18, 2011 9:08 PM

Quote:

Originally Posted by Fritzdude (Post 5246118)
However, you can take comfort that at least you won't have to worry about a moose walking out in front of you.

That's why I'm voting Palin.. she'll fix that problem for all of us who can't travel elevated.


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