Brad Ideas - Hybrid Personal Rapid Transit - Comments

PRT people say dozens of

Anonymous — Tue, 11 Sep 2007 05:43:01 -0700

PRT people say dozens of vehicles can go around dozens of rails under computer control. If this is the case, why aren't there been many, many cases of single vehicle, single rail projects are being computer controlled? After all, computer controlling a train going back and forth on a single track should be EASY. That would save money, right?

Not even this is being done, but somehow the PRT True Believers tell us the much more complicated case is the next step. Shouldn't they be able to point to successful computer controlled trains all over the place if they are that great?

Yup

brad — Mon, 27 Mar 2006 20:06:42 -0800

This is considered one of the difficult PRT challenges. A baseball game is even worse than a train station. You could have a very long spur at a high capacity station, or even a spur with its own spurs where cars can presumably move in and back out. You would also have to have fancy algorithms to create gaps in traffic going past the big station to accept all the traffic. Ideally it would leave in bunches, sort of like trains but uncoupled.

Or you would of course, have to have long waits at such stations from time to time. Which is what we have now with shared transit, after all.

Re: Question about loading during rush hours

A Transportation Enthusiast — Mon, 27 Mar 2006 06:18:08 -0800

This is called, I believe, the "pulse" problem, where you get an extreme surge of demand. In general, there are two scenarios to consider:

(1) The typical rush hour rush, where people don't all leave work at the exact same time, but there is a general rush between the hours of 4-6PM, peaking on the hours. For line haul systems, people from a relatively large area aggregate and wait in the station; they don't all arrive at the station simultaneously, but they depart simultaneously because during the wait for a train, the station fills up. So the pulse in this case is not as severe as it would seem: the "pulse" in the station is actually due more to aggregation of people waiting for a train. In the case of PRT, there are two significant differences: (a) people arrive and immediately leave, so there is little aggregating. Some may have to wait in a short line during the heavier times, but with good design this is generally shorter (in the average case) than waiting for the next train to arrive. (b) PRT designs generally have more closely spaced stations, so the load is more spread out. Instead of, say, 1000 people arriving at one station in 15 minutes, you have 250 people arriving at 4 different stations.

(2) True "pulses", i.e. after a sporting event. When you have thousands of people exiting simulataneously from a sporting event, this is an extreme pulse that would place demands on any system (light rail, buses, cars). That's why there are traffic jams after sporting events, because the road system can't handle the pulse. PRT designs I've seen would handle this by building several larger stations at the statium itself to handle the anticipated loads. In other words, a stadium is where you'd expect to handle large crowds, and you'd also assume that a stadium would have the space to allow for several larger PRT stations. So there are ways of alleviating it, but there will still be delays after a sporting event, just like any other mode.

Question about loading during rush hours

DennisSt — Sun, 26 Mar 2006 09:03:47 -0800

This is the first time I've seen a site like this. I've been pondering a system like this for years during long commutes but didn't realize it had a name or following.
The question I have is how do you prevent these vehicles from blocking main lines when you have 50 to 100 (or more) people requesting their individule cars at one time/station? I presume that you would load people on a side spur then wisk them away to the main track(s) but when many people want to leave from the same terminal at the same time (such as with current mass transit) it seems to me that there would be a stack up on any given spur and then a major bottle neck to the whole system since this same scenerio would be occuring up and down the line. (I've enjoyed this discussion and would encourage nay-sayers to put their energy to solving problems rather than tearing down other's ideas!)

VERY old tech

Richard — Thu, 23 Mar 2006 04:11:17 -0800

Anonymous stated:
"Technology that works usually gets started right away, planes for instance, 20 years after the Wright brothers they were all over the place."

Yes; 20 years after the Wright's, planes were everywhere. But your observation misses the preceding 400 years at minimum of mans' attempt to get heavier-than-air vehicles to work. I can start with the drawings of at least da Vinci; perhaps there were even older plans for flying craft. Yet persistence over all this time, coupled with incrementaly advanced technology over succeeding centuries, and despite MANY tremendous failures (and self-rightous naysayers by the dozen), have given us the ability to cross the world's oceans in mere hours. Clearly, the technology did not work nor get started right away, and yet here we are using it to great advantage nonetheless. Pick any advancement technologically, and I'll bet the same can be said about it.

About 6 years ago, I had a private musical instructor who was highly doubtful of the power of the internet to do anything worthwhile. Yet here we sit discussing the finer points of the persistence of man to overcome obstacles to create the world in his vision, using the internet. And I'll bet Jeff Bezos would disagree with my former instuctor, not to mention the untold number of people making use of Ebay.

Furthermore, I will also mention that anyone of great success will tell you that failure is the path to success. Edison, Trump, Kiyosaki, Tesla - you name it. Today's failure is a kernal of truth, a moment for reflection - "why did this fail today, and what can I do to fix it the next time?" Edison tried over ONE THOUSAND different ways to make the concept of a lightbulb a reality. He did not stop at iteration 2, or 10, or 138. He continued refining his materials, technique, and technology until he made it work! Continuing in this vein, I would also like to point out our (U.S.; western) concept of government as envisioned by the Founders. A limited constitutional republic, which has been the bright light for the world for over 200 years. It can be argued that governance is a form of technology, and yet after all of these 200+ years, there are many nations out there that haven't accepted this form organization, despite what most of us would agree (yeah, it currently has some ugly bugs, but still...) is the best damn state of the art for freedom, prosperity, and individuality there is. Your line of reasoning, in essence, would therefore consider our freedom a "failure" since it hasn't become as widespread or as "free of flaws" as you would like to see.

Propaganda

A Transportation Enthusiast — Wed, 22 Mar 2006 18:45:59 -0800

They cannot argue on technical merits, so they argue that "it hasn't worked for 40 years, so it never will". It's pure propaganda.

Judge PRT for yourself, here

old tech

Anonymous — Tue, 21 Mar 2006 14:14:18 -0800

Technology that works usually gets started right away, planes for instance, 20 years after the Wright brothers they were all over the place. Radio, computers, telephone, trains, this is an example
repeated over and over. See the pattern?

PRT and blimps on the other hand are a bit limited in acceptance and
availability. Shriveled tendrils on the branch of tranport evolution.
DEAD TECH. No hoping for the next "breakthrough" is going to make
PRT work after 40+ years. WVU Morgantown is the goodyear blimp
of PRT. Kind of works, but cost a mint, and does not really work, with limited service and a captive audience.

40+ years is a long time for a tech to "almost" work.

horseless carriages and aeroplanes

Anonymous — Fri, 17 Mar 2006 03:37:18 -0800

At the dawn of the motor age, many municipalities steadfastly refused to accept the new vehicles on their roadways - passing laws against them for all manner of reasons: the unproven technology, the noise scaring horses, the excessive speed, the smoke, whatever they could come up with out of unreasoned thinking. Same goes for heavier-than-air aircraft; many thought the technology would never reliably work and carry people safely and efficiently. Heck, the use of a radio in a vehicle was once illegal in many states when they began to be incorporated into production. Not to mention that at that same time, 25 miles an hour was considered a hell of a speed. Can you imagine going back in time and telling people that cars in the future will easily attain speeds in excess of 100 MPH, and that we would be regularly driving as fast as 60 MPH with other vehicles traveling in the same and opposite direction at similar speeds without any barrier between - down to sometimes as little as one foot apart. If you were to share this with people from the past, you would surely be rebuked and ridiculed and run out on a rail, same as rabid anti-PRTer's do today.

I suspect the animosity results from a fear that PRT would become yet another government enterprise like regular public transportation: incapable of becoming self sufficient without continous taxpayer subsidy. On this I would agree - I also don't want socialized, subsidized transportation. However, today's road and highway system surely isn't self supporting either, being funded in large measure by tax revenues which are not based in any form by actual road usage (true, gas taxes are use-based, but the larger remainder come from income and property taxes). I'll state it again: when private enterprise can support the construction and maintenance of such a system (you and I as individuals are a part of private enterprise) without taxpayer funding, this kind of concept will flourish - just as it has for the automobile industry in years past.

No assumptions

A Transportation Enthusiast — Thu, 16 Mar 2006 21:14:09 -0800

"On the other hand, it can also be foolish to assume that the reason everybody before you failed at something was because they were all stupider than you."

There's no assumption here. When systems fail, engineers analyze the reasons why, and fix them in their future systems.

I've done some reading on the Denver system. The issues were primarily poor engineering. For example, the bags had to be loaded onto carts a certain way, or they would fall off on the curves. This was poor design: either the carts needed to be better engineered, or the curves should have been less severe.

In some ways, I think the fact that it was baggage, not people, actually hindered the design. If they were designing for humans, they wouldn't have designed a system so fragile.

I've read a lot on PRT, and I've seen nothing about it that is technologically infeasible. There are certainly engineering challenges, but many of them have already been solved. All that remains is some field testing and a commitment to build.

In other words, the main issue that PRT must now overcome is public acceptance, and that's turning out to be the biggest hurdle, by far.

Failures say

brad — Thu, 16 Mar 2006 20:11:21 -0800

I think it's fair to say that failures at certain tasks suggest those tasks are harder than people imagine. They are certainly a reason to be wary and to look harder, and to learn the lessons from a failure. But they don't prove something impossible.

On the other hand, it can also be foolish to assume that the reason everybody before you failed at something was because they were all stupider than you. Sometimes that's true but not always. The baggage system was not a PRT, but it contained some technologies people want to use in PRT. Certainly a working PRT system could be easily reworked to deliver bags to destinations as readily as it delivers people. Probably too expensive a way to do it, though. Deliverying people should be much more expensive than bags in almost every way, and cheaper only because people enter and leave the cars under their own power.

Regardless of who you are, your message is still propaganda

A Transportation Enthusiast — Thu, 16 Mar 2006 19:17:43 -0800

There is a fundamental point you seem to be missing: the failure of one engineered system does not invalidate the underlying technology. The Denver baggage handler was a dismal failure of design and engineering -- it does not mean that all automated systems will suffer the same fate.

Here's a classic example of spectacularly bad engineering, with a truly catastrophic result. Does this incredible failure invalidate all bridge designs? Of course not! In fact, after the collapse, they redesigned that bridge and it's stood for over 50 years.

Your argument is inherently technophobic, and it has no relevance. I'll say it again: the Denver failure was a failure in design and engineering, and has no relevance to the underlying technology.

And, by the way, if you want proof that automated, PRT-like systems can work, look at Morgantown: automated operation for over 30 years. And even though Morgantown is not true PRT, it's closer to PRT than Denver's baggage system.

See Wikipedia for links to the Morgantown system -- again, not true PRT, but neither is Denver's baggage system.

Sir. you are mistaken.

joe 14pack — Thu, 16 Mar 2006 15:07:10 -0800

I came up with "faith based transit" and many people liked the phrase, apparently Mr. Avidor likes it too. That is OK, it fits PRT and is now a PRT synonym. Mr. Avidor does not come up with all
the great sound bytes. He is more a visual artist.

The Denver Airport Luggage Handling Fiasco (PRT for suitcases)
is the engineering lesson that civil engineers and city-county-state officials will recognize and pay attention to, a public investment of hundreds of millions for many years that was a complete failure that cost the public huge losses.

No civil authority will put reputation, public safety and
financial ruin on the line for this Jetson cartoon fantasy after looking at the history of the Denver Airport PRT luggage handler.

PRT is a dead technology.

I think it mostly solves it

brad — Wed, 15 Mar 2006 01:21:22 -0800

Clearly many people will rent out their vehicles if they have a station near their home or work. For a large chunk of the population, it would mean the difference between owning your own vehicle at a price you can easily afford, and always renting.

However, for those that don't, you need parking, but you don't need it really close to the station. (Though the closer it is the more quickly you can summon it on short notice.) You can park somewhere that the parking is cheap, and you can park the vehicles very densly compared to cars, with a slight extra delay. Probably 3-4 times the density of cars if they are smaller and can also be stacked vertically in spots 6' high, and like valet parking.

For the commuter who knows they need their car around 5pm, the system can prep the car in advance and have it waiting at the station. However, for the typical office worker, you would issue a computer/cell command when preparing to leave, and in the typical 5 or more minutes getting in the elevator and walking a short distance to the station, the car should be very close to being there, if not there already.

Office buildings might also build large "parking stations" in their buildings, using some of the space that was allocated to cars. As noted, I expect at least a 3x density improvement, and this gives a station in-building with instant access to your vehicle.

There's also another kind of "rent" possible with vehicles, namely within the family. Car takes parent #1 to work, returns to home station (though not to home garage quite yet) for use of parent #2 or kids or whatever. And kids of course can mean even young children if they don't leave the automatic track area. Those kids can probably bike to the station, for example.

dual mode

A Transportation Enthusiast — Tue, 14 Mar 2006 23:29:12 -0800

The problem I have with dual mode is, it doesn't solve the parking problem. One of the benefits of PRT is that the vehicles are reused, but if you have privately owned vehicles on the guideway, you still have to have places to park those vehicles.

If you're not Avidor, then he's trained you well

A Transportation Enthusiast — Tue, 14 Mar 2006 19:21:34 -0800

Mr. Anonymous: You are quoting almost verbatim from the Avidor creed, right down to his buzzwords like "faith based transit". So you are either Avidor himself or one of his apostles.

But, anyway, who says it is irrelevant -- the point is, this is the same tired old message that Avidor has been pushing for years now. These points have been discredited countless times on dozens of forums, but he remains obsessive about continuing to spread them, like gospel.

If you want these types to go away, just challenge them to a debate on a technical topic, like PRT safe headway. They'll spout some ridiculous talking point and then disappear with an excuse ("I don't have time to debate this crap"). I've seen it so many times I can almost recite it by heart.

Anyway, if you don't believe me and want a neutral assessment on PRT, once again I suggest you take a look at the Wikipedia article. There is a very nice technical summary there, along with many links to the history of PRT development.

Hybrid Personal Rapid Transit

brad — Wed, 08 Mar 2006 14:45:30 -0800

When I was in high school, I did a project on PRT — Personal Rapid Transit. It was the “next big thing” in transit and of course, 30 years later it’s still not here, in spite of efforts by various companies like Taxi 2000 to bring it about.

With PRT, you have small, lightweight cars that run on a network of tracks or monorail, typically elevated. “Stations” are all spurs off the line, so all trips are non-stop. You go to a station, often right in your building, and a private mini-car is waiting. You give it your destination and it zooms into the computer regulated network to take you there non-stop.

The wins from this are tremendous. Because the cars are small and light, the track is vastly cheaper to build, and can often be placed with just thin poles holding it above the street. It can go through buildings, or of course go underground or at-grade. (In theory it seems to me smart at-grade (ground-level) crossings would be possible though most people don’t plan for this at present.)

The other big win is the speed. Almost no waiting for a car except at peak times, and the nonstop trips would be much faster than other transit or private cars on the congested, traffic-signal regulated roads.

Update: I have since concluded that self-driving vehicles are getting closer, and because they require no new track infrastructure and instead use regular roads, they will happen instead of PRT.

Yet there’s no serious push for such systems…

Read on.