--"Explain then, how PRT won't have bottle necks at stations and on-ramps and off-ramps and interchanges between lines, just like cars."
Bottlenecks are caused by too many drivers deciding to take a certain route to their destination. Our highways and freeways are designed to create bottlenecks: roads feed to highways which merge into freeways; more and more traffic jamming into a limited space with each passing mile.
In a properly designed PRT system the elevated guideways would be laid out in a grid pattern with several different paths to get to your destination. Since PRT auto taxis are 100% computer controlled the rider cannot choose which way to go: the computer decides the route each vehicle will take to minimize traffic on each guideway. On-ramps and off-ramps are handled by the computer slightly slowing the proper vehicle to give your auto taxi enough space to merge seamlessly in with the traffic. The SkyWeb Express company has built a mini-scale working model of this to demonstrate the seamless computer control of vehicles entering from on-ramps and exiting via off-ramps with perfect precision.
--"Try to envision the logistics of an entire city with 10% or more of its commuters riding PRT and going to all different places."
That would be easy for modern computer systems that can calculate things down to the nth degree. Simultaneously controlling 60,000 to 200,000 vehicles would be like childsplay for state of the art computers that are used for calculations involving billions of particles. Google computer simulation of fluid dynamics and weather...
--"Envision the system of overhead tracks required to cover an entire metro area. Envision how the stations would work with pods going in and out. What would happen to the unused pods? How would you prevent pods from piling up in one place and being insufficient for demand in another?"
You may know this already but stations in a PRT system are "off line" and do not hinder passengers whose destination is farther down the line. The side track that takes your auto taxi off the main line and to the station can be any length desired, so for very busy stations like at a factory, mall, or a busy downtown office building the "off track" would be very much longer than one for a PRT station in your neighborhood. Thus, it could handle more vehicles lining up to pick up or drop off passengers. Some PRT designs allocate a turn out for each auto taxi berth (where passengers enter and exit). Other systems envision a series of queues where passengers can choose the shortest queue but have to wait for all vehicles ahead of them to depart before an empty one can approach. There are positives to both design choices and negatives as well, the former being more expensive because a separate track section is needed for each berth, the latter being less convenient because one would have to wait for all the filled vehicles to move away from the station before an available one could pick you up.
Unused pods would be controlled in the same way as those carrying passengers. Just as your DVR knows that it has to record "The Simpsons" in the next minute or so, the PRT system computer would know where passenger requests have been submitted. There should even be an option to have an automatically scheduled pickup at a certain place and time (e.g., being picked up at home each morning at 7:15 so you can make it to work by 8:00). I wrote an entire 6 page explanation of this in a letter to Bill Gates and Steven Chu. In a nutshell, if there is a passenger needing a ride the computer will dispatch the nearest empty auto taxi to that station and that berth.
Rush hour would necessarily leave thousands of auto taxis in the downtown area so adequate "staging" facilities would be needed since all of those people will likely be needing a ride home at the end of the day. I proposed in my letter that several "staging areas" would be built at various locations around the metro area to park empty auto taxis as well; this would increase the number of vehicles required but would guarantee fast service pickup. If an excess of "empties" accumulate at one location then some of the auto taxis are directed to a different nearby staging facility, thus alleviating any excess at one location. A careful and detailed ridership survey would be taken before, during and after construction to ensure that these staging areas are of the proper size and new ones can be added at any time in the future.
--"How would you prevent traffic jams on the equivalent of on-ramps and off-ramps? What if a rider wanted to go from one heavily-used line to another?"
These two are answered above... don't want to duplicate.
--"You might think that PRT has the "advantages" of the automobile (and not sitting next to one's "inferiors" is a reason that people often cite) but it also has the same disadvantages, other than lack of emissions, and potential for getting stuck in jams."
PRT proponents do not object to sitting next to one's superior or inferiors, we simply believe that one's time is more productive when one has the choice of riding companions. The auto taxis carry either 3 or 4 passengers depending on what company's design you're talking about so coworkers could "pool" together to share the ride, perhaps do some brainstorming or productive work on the way in to the office or just get their socializing out of the way so work time can be used for "work" and not chit chat about the big game or the episode of that talent show or whatever. The key is, you choose if you want quiet alone time or time with friends, family, coworkers or strangers.
Traffic jams are for cars, caused by drivers making poor choices. As I described above, PRT is computer controlled and has multiple paths to the same destination so there will be no traffic jams.
--"Plus, it's not even as mobile as a car. Unless you're going to send lines to everyone's house, it's no more convenient than a bus or train."
Actually, that is exactly the recommendation that I made to Bill Gates and Steven Chu. I find the current PRT companies to be lacking bold vision for their revolutionary product. They do not want to step on any toes, go out of their way to avoid the impression that their system would compete with light rail (thinking they won't make enemies that way). What they may not know is that the light rail industry knows its product is inferior and a bottomless pit for tax payer dollars. Light rail is gunning for PRT and has been since the 1960s when PRT was first proposed. I say "full steam ahead" with PRT and if you step on a couple of toes then so be it. They aren't winning any city-wide contracts with the meek and mild approach they are currently trying.
So, heck yes, PRT track to everybody's house. I envision the elevated portion forming a grid with each elevated guideway being 1 or 2 miles from the next one, a 2 mile grid spacing. The grid of elevated guideways thus forms rectangular areas inside each grid segment. For these I propose the roads be torn up and PRT track be installed at ground level (or only a couple feet above it so as to avoid city water, sewer, electric lines, etc). This ground level guideway will operate at a low speed, perhaps 20 mph and each auto taxi will have collision avoidance and pedestrian detection built in so a stray child or a stray dog can't become the next tragic story on the 5 o'clock news (bad press). And you will get picked up right out front of your house or apartment building and dropped off exactly there on the way home as well.
That would make PRT just as mobile as a car but some neighborhoods may still want to keep their cars so perhaps only one side of the street would be torn out and the other side becomes a one-way street. I'm agnostic either way. Personally, I'd rather live in a neighborhood without any cars but others can make their own choices.
On-ramps and off-ramps would be provided to one north-south PRT guideway and one east-west PRT guideway so the computer can choose the most advantageous route for you to get on and off the elevated guideways. The exact length of those on- and off-ramps and how steep they are would have to be studied to reduce discomfort as much as possible.
--"Either PRT is a deliberate attempt to sabotage public transit (which mysteriously works every but the U.S., where people have a sociological prejudice against transit and a belief, carefully cultivated for 70 years by the auto companies, that cars mean "freedom.")"
As I stated above, all of the PRT companies go well out of their way to state that they do not want to compete with light rail or buses, even going so far as to suggest PRT as "feeder" networks for bus or train stations in the 'burbs. I find this milk toast approach to be too limp an offering for anyone to take it seriously. I believe in bold measures, bold solutions to the serious problems facing our society. Thus, I find the PRT companies' lack of backbone, lack of vision to be off-putting. Seize the day! I, personally, wish PRT would replace light rail and bus service and the light rail industry and bus line industry knows that their tax dollar-sucking failure machine cannot compete against PRT so they have managed to scuttle each and every PRT project that has been proposed. PRT companies try not to make enemies; they just don't realize that their very existence is a threat to the inefficient and inconvenient 19th century light rail and bus industry. But that's just me.
--"Many of us feel the opposite. I lived in Portland for 10 years without a car. At first I was the only such person I knew, but within those 10 years, five of my friends gave up their cars, and the local paper wrote of young people who were in no hurry to learn to drive, because the transit system was so convenient and cars were so expensive."
Good for you! I rode public transport here in Dallas every day. It took 4 times as long as driving (2 1/2 hours) each way due to the number of transfers I needed to get just a few miles away.
--"Phenomena like that TERRIFY auto companies. That's why they push investment in fake transit projects that will never really work and can be used to "prove" that cars are better."
You mean like light rail projects that cost hundreds of millions of dollars per mile and never service more than 5% of the population, while soaking the tax payers for all that they can get each and every year? I must agree with you. Light rail and buses are the auto companies' best friends. All of my friends who used to take the bus or train have since broken down and bought cars because of the service interruptions, total schedule failure in even the lightest snow storms, and generally excessive amounts of time required to get to work and back.
--"Oh, by the way, I looked up existing PRT projects. All of them are single short lines or loops. There are none with interchanges."
Check out JPODS, Vectus, SkyWeb Express, and
http://www.innov8transport.com/As I stated above, I get the feeling that they want to propose small, limited systems to keep initial costs down and not "scare off the buyers" while at the same time posing no threat to the entrenched interests of light rail and bus lines. I've already stated why I think this is a losing strategy and PRT, by its very existence, is a threat to light rail and buses so that is just a lack of spine on their part. To the victor goes the spoils, as they say. I think they should be much bolder, propose much grander plans. But they aren't so...
If you are interested, I've posted my letter to Mr. Gates elsewhere on DU and it would be easy to find via google: Gates PRT
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