Thursday, August 27, 2009

48> PRT Stations...Continued

Almost immediately after posting last week I realized that loading cars one at a time was probably not what the designers of “taxi stand” (serial) stations had in mind for crowded situations. By loading a group of PRT vehicles at once, they may depart as quickly as the leading vehicle is ready, a fact that was quickly pointed out in the comments.

In particular, alert reader Akauppi added a link to a fairly comprehensive study of the subject by Peter Muller of PRT Consulting, who pointed out that numbers of simultaneously loaded vehicles could depart in “platoons”. The study concentrated mostly, however, on what he termed “open guideway systems” such as Ultra, because of the many ways they may be maneuvered. (These systems are essentially automatic cars, and may be parked and boarded in any way a car can.) In a statement reminiscent of criticisms that I have also made, Muller states, “Captive bogey PRT systems, such as those being developed by Vectus and Skyweb Express, show little variation in station design. The stations are always off-line, and the bays are always arranged in line with each other. This lack of variation probably results from the intended relative high capacity of these systems and their inability to accommodate tight radii.”

The obvious countervailing argument is that those “open guideway systems” fail to address one of the obvious benefits of most PRT systems, that being reduction of roads. We are rapidly coming to a time when we will have electric cars. Does separating precious real estate for less nimble automated ones really solve anything? Isn’t a separate road less efficient than just widening the one that’s already there? Well that’s a different subject, so I will return to what he terms a “captive bogey” system. (Pod on top of a rail.)

I did have one idea on this subject, which I have not seen, and that is this. The necessarily elevated stations, such as is required by the PRT International and Skyweb Express systems, must include an elevator (for the disabled) a feature I have criticized in the past as not being repeatable throughout the suburbs, for cost reasons. I think it noteworthy, however, that such a system, in the inner city, may have a very small footprint at sidewalk elevation. The sheltered area below the station might actually be an asset, as it could house news or food stands, or other sidewalk vending, at a natural spot for pedestrians to congregate. (No, that’s not the idea.) The idea is this. The “offline track” can be further split in two with the elevator in the middle, its structure supporting both tracks and a common boarding area, which needn’t cross any track. It would look something like this.

In this picture the large E is the elevator, which has two doors, ED1 (elevator door 1) and ED2. This is how it would work. The elevator, at street level, would open ED2 and passengers would be lifted to the boarding area, and ED2 would reopen, letting them board. ED2 would close and ED1 would open to let arriving passengers into the elevator, which would descend to street level and open (ED1) to let arriving passengers leave. ED1 would then close and ED2 would open, starting the process anew. Back on the boarding level, green and red lights, or even gates would be indicating the available vehicles, starting at the front of the line. The vehicles could move out as a platoon or the front vehicle could start out when ready. Once passengers have disembarked the vehicles on one of the tracks, the now empty vehicles in the arrival area would move up (to the boarding area) as a group.

In a hanging (gondola) system, a similar design can be used at street level, without the elevator. Very highly trafficked areas could have an elevated level as well, so that the station would, by the berth count illustrated, be capable of 12 simultaneous loadings and 16 unloadings.

Finally, here is a depiction of dual docking track described above, but with the “saw tooth” boarding scheme favored by Mister and Ultra. (fig. 1) Note that passengers may either board or disembark from any berth. The saw tooth design, being inherently parallel, gains less from splitting the track into two than does a straight line (serial) arrangement.

Actually the long, narrow footprint of a single row of berths probably fits better into the available space of most sidewalk environments. (fig. 2) Each vehicle may leave immediately after boarding, but both departing and docking vehicles may have to wait for each other because this system requires backing up into potential traffic to leave the station. A good way to control traffic would be alternate between groups of vehicles entering the station and groups leaving, (like the previous example) rather than a pure “first come, first serve” basis. In Muller’s study, he suggests that all vehicles can pull out together, ignoring the issue of vehicles not being ready at the same time. I would suggest perhaps three at a time. (In fairness, he showed a three-berth station) I should also note that with a gondola design, with no slots in the floor to step into, open-air stations could be extremely cheap, and therefore positioned with much more frequency than other station designs I have considered, and therefore could be made with fewer berths. (I am a big fan of cheap stations) Going back to the original, hypothetical three-station loop, however, it would seem that “platooning” is increasingly advantageous as traffic increases, but is a drawback if the traffic is minimal in “saw tooth” stations. Note that in this system, the berths are not exactly equal. Vehicles in the front berth, for example, would have little problem leaving but when empty the front berths could have slower vehicle replacement times. The opposite would be true for berths in back. Optimal traffic management for very busy stations would seem to be relatively complex. It is not immediately apparent to me if the saw tooth design would have better throughput than the dual track strategy outlined above, but I think it would out-perform the single line “serial” designs (PRT International, Vectus) with ease. I would also point to the variation of the saw tooth design I pictured in the last post, would not require platooning but requires rapid elevation changes in the track to avoid pedestrian/vehicle interference. It would seem to call for a comparatively large station, if the number of berths was, say, less than eight, but would be a very compact and efficient way to arrange a dozen or more berths.

In conclusion, I would reiterate the observation of the last post, that in order for PRT to be a valuable transportation alternative in initial limited and trial situations, high capacity stations are a must. In these posts I have explored the ideas of boarding and departing in groups and splitting the offline track as a means of increasing station throughput. I have not exhaustively studied every possible way to achieve simultaneous parallel “processing” of passengers, but it seems that PRT can have passenger turnover rates approaching group transit alternatives.

I also believe that a mix of both high capacity and very inexpensive suburban stations or stops is required to have a system capable of reducing commuter traffic, and that most current PRT designs do not meet this test. I hope that consideration of these station alternatives will prompt a reexamination of PRT vehicle design, especially with regard to both vertical and horizontal turning radii.

Alert read cmfseattle sent us this link to an article written by Bill James, (Jpods) a fellow who has come up with some designs (track and bogey), which are so much like mine it’s spooky. (And he seems to have done it first, but who is counting?) What is very cool is his trademarked term for PRT, the “Physical Internet.” Very descriptive, don’t you think? Let’s agree on something just that versatile and unstoppable.

21 comments:

Anonymous said...

"What is very cool is his trademarked term for PRT, the “Physical Internet.” Very descriptive, don’t you think?"

Except we don't have the luxury of allowing dropped packets.

cmfseattle said...

"Except we don't have the luxury of allowing dropped packets."

there's a joke in there somewhere about automobiles, but anywayy...

check out this taxi2000 light rail transfer animation.

also: i'm having no luck finding it right now, but somewhere on skyloop.org i think, was a document mentioning the concern that elevated station platforms would be difficult to patrol from the street.

akauppi said...

The animation is interesting.

First of all I think the (sequential) station type is the wrong selection here. But that aside, it shows nicely how the availability of free vehicles can become the bottleneck.

In the animation, they happen to flood in nicely. But think if the boarding was faster, there would be no free vehicles to board.

There are solutions to this, s.a. keeping a legion of free vehicles stored in a nearby storage warehouse, for i.e. sports events or concerts to end. But the number of such vehicles is pretty damn big. About 1500 would do in my home town. :)

Then again, currently those people have around 1500 cars at the parking lot.

resonance said...

Parked (stored) PRT vehicles take up a heck of a lot less space than lot- or garage-parked automobiles, even if the vehicles are the same size as automobiles (which they're almost universally not). Besides the space between parked cars, it would seem that one third to one half of a parking lot's total space is devoted to lanes or aisles to access individual spots, which are entirely unneeded for PRT, where the first vehicle in a line can simply be popped off the queue and sent out for a pick-up.

Anyone have more precise figures for the estimated parking footprint for a given number of vehicles for different PRT system designs? How would a system like Skyweb express handle multi-level parking (which I'm sure will be necessary for dense urban storage)? Are vehicle elevators necessary, or even practical? Strangely I don't think I've ever seen a mock-up, schematic or actual photo of what the storage facilities would or do look like for the different systems. Perhaps LHR ULTra is such a small system that it doesn't need any storage beyond what the stations can accomodate, and that will probably be the case for most of the initial systems, but there should still be a plan for it. Do any of you guys have such info for that or other systems?

Dan said...

Dan The Blogger Is Overwhelmed-

Thanks for the humor A. – cmfseattle, great addition to the topic! I watched it again and again, stopwatch in hand.
Akauppi, Resonance, I’ve got to short-change the storage thing for the moment. Let me sleep on it. Otherwise I’ll never post this lengthy comment that I wrote earlier…

The animation has no occupied vehicles coming in, and has no disembarking area. It is also extremely speeded up. I don’t know if it is cued to a real time clock or computer cycles, but on my old laptop, it takes 2.5 minutes to clear 108 vehicles, about 12 seconds each. That includes the vehicle pulling up, the door opening the person entering the vehicle and sitting down, the door closing and the removal of the vehicle from the area. If the incoming vehicles had passengers, the “yellow time” would be a lot higher. One single elderly person could bring that station to a halt. Also, if the vehicles park, say, every eleven ft. that makes the boarding area about 100 ft. long.

I know this is just a basic animation and not a real simulation, but it shows some of the issues I tried to address with parallel boarding. What would the turnover be in the real world? Let’s start at the beginning. You’re next in line, and your vehicle is on the way, accelerating toward you as the one from your berth speeds away. How long does it take it to get to you, stop, and open the door? I would think 12 seconds would be on the fast side, but let’s go with it. The gate opens. (It would need a gate if cars advance and park from up to a hundred ft. away in 12 seconds, right?) The door opens and you enter, sit down, and push the ready button. The door closes. Now you wait for the slowest boarder in line to be ready. You’re in luck. You’re surrounded by impatient athletes, so you only wait 5 seconds. How long did all of that take? It has to be 15 seconds, doesn’t it? Now your car starts. 3 more seconds and you’ve cleared the berth. Time trial over. Result? 30-second turn-around. Nine passengers away. That’s 18 per minute, and remember, that’s without anyone disembarking. Compare that to 100 ft. of empty subway pulling up for a minute, with 2 doors on each car, and you see the problem. True, the subway won’t take you all the way home, but neither will PRT without a well developed network – and let’s face it. PRT will never start with a big network. Finally, what about people arriving? Well, in order to get the vehicles empty before the boarding area, to keep the 18 passenger per minute turnaround time, the station would need to be another 100 ft. long or 200 ft. total. That is a very large structure. If the same berths are used then add another 20 seconds (minimum) to the turnaround time. Now it’s 10.8 passengers per minute. I’m sorry, but that is simply pathetic. We’ve got work to do.

Anonymous said...

First, I agree that time must be compressed in this simulation (the train is only stopped for about 20 seconds - what would be normal? One minute? 2 minutes?)

Second, all the disembarkees head directly for the PRT & queue up. Would this be normal behavior? Maybe so. Commuters would probably have secured the most effective form of payment (smart card, RFID card, etc) & would know their destination code by heart. They wouldn't have to stop at a kiosk to purchase a ticket - and those who would could be presumed to be last in line for the purposes of the simulation.

Third, because this is a Rail transfer point & the arrival times of the trains, & the average volume of passengers, would be known from previous history, the approximate number of cars needed & the time when they'd be needed should be known to the system & would be made available - either from other station's unused capacity or from reserve capacity.

Fourth, because this is a high volume station, it would make sense that people would disembark at a separate area and the empty cars looped around to the embarkation platform.

Dan said...

Dan the Blogger Responds- Finally!

Anonymous, I owe Akauppi and Resonance a response from a couple of days ago, so I’ll be uncharacteristically brief. Your 2nd point - I think kiosk activity would be a confusing distraction from the animation, and is irrelevant, anyway, because more can be added, or there can be prearrangements, as you said. Point 3. That’s an interesting observation because it points out how easy it is to assume that a huge network already exists, when planning for one that has yet to be built. In the short term, one cannot assume the existence of 99 replacement cars being within a 2.5-minute radius. Point 4. It really isn’t high volume at all. 10 waiting shuttles could do the job just as fast. “But,” you say, “those ten shuttles might not be going where I want to go.” Problem is, neither will PRT until a whole network is in place.

About perfecting pod parking…
Akauppi, Resonance, your references to parking bring up a point that really is worthy of its own post, if not a couple. I think the problem, as I mentioned to anonymous, is that PRT advocates tend to look to the whole completed network to answer a short-term problem. In a system with many thousands of cars and high track density, extra cars can be called up from all over. In the short term, however, we are confronted with a less “PRT friendly” system architecture. Instead of the self-balancing that comes with scale, we have a limited hub-and-spoke system. Sometimes I wonder if PRT promoters pick routes with balanced (both directions) traffic flow in which to do their simulations. For whatever reason, nobody seems to talk about the kind of storage that is required to address the highly unbalanced demand created by large buildings, stadiums, etc.

Clearly the storage means would be totally different for the different designs. I think PRT International, Vectus, to name a few, would (for reasonably small footprint parking) probably need elevators, which, I presume, would involve a section of track that could be raised and lowered. The Ultra and 2getthere designs would probably use winding ramps similar to multi-level auto parking, I think Beamways and Skytran would probably do the same but they wouldn’t require floors. Mister and similar systems, like my own, could be stored in tightly packed geometric arrays. (Smirk) ;o) Frankly, I think that PRT providers don’t want anyone thinking about hundreds of unused pods in storage, because that’s not the best part of their business model. I agree, however, that we need them, and ought to bring the matter of unbalanced traffic loads up for discussion.

cmfseattle said...

"Problem is, neither will PRT until a whole network is in place."

which is why PRT shouldn't be expected to handle big-box flows from the outset. too much traffic would be a high-class problem to have.

this is where the importance of a business model comes into play. each segment or upgrade should be added after the current ones have been successful. the biggest reason PRT hasn't attracted VC is the amount of risk. which is why ULTra has been so successful; they've always been on-time and on-budget.

their station design is modular.
http://www.atsltd.co.uk/Bath/competition-details/stations/

i understand that you want to make sure PRT isn't shooting itself in the foot by not planning to handle large flows. but there is no silver bullet. sometimes, you need trains.

Bryan Williams said...

PRT stations and being able to move a lot of people simultaneously has always been a hurdle.

There are two things that I have to keep reminding myself, #1 Well designed PRT is in constant motion, #2 rides go direct to desired destination.

Current mass transit is setup to build up a mass of people and then move them. Except for events where people are all released and hitting mass transit at the same time, typically people arrive at terminals at different times. In the current system, those people arrive and wait until the train comes, building up a mass and then taking them all together. In a well designed PRT system, that mass quantity is less of an issue because there is constant motion. The group isn't growing like it would in the current system because the group is always being lessened by people leaving as others are arriving.

The second thing that occurs to me with a PRT system is that once you're in your car you, go directly and personally to your destination. That type of service I feel is worth a slightly longer wait in a station. The alternative is getting onto a crowded subway and then stopping every 3 minutes as more people try to pack themselves into an already full car. A slightly longer wait is well worth being transported personally and non-stop to my destination.

Don't get me wrong, I would love to see a station design built to handle rush hour traffic efficiently, but let's face it PRT isn't magical. There are drawbacks to current transportation as well.

Anonymous said...

"Point 3. That’s an interesting observation because it points out how easy it is to assume that a huge network already exists, when planning for one that has yet to be built. In the short term, one cannot assume the existence of 99 replacement cars being within a 2.5-minute radius."

I think it is reasonable to assume that the simulation is for a mature system that has wide coverage, otherwise the "sims" would mostly exit, stage left, to the bus stop or park'n'ride and only a small number would queue up to take the PRT to the destinations that it served.

"Point 4. It really isn’t high volume at all. 10 waiting shuttles could do the job just as fast. "

By 'shuttles' do you mean busses?

Dan said...

Dan the Blogger responds-

Cmfseattle, Thanks for the link. I guess they would be a little ticked off if I replaced the guideway with a monorail for hanging PRT … About Ultra; I do not know their business model, but it seems to me their principle competition would be human driven vehicles, which I think I heard were prohibited from the area for some reason. Anyway I am a bit suspicious of the suggestion that they represent a compelling business model. Do we know what they charge, or how long it will take to pay off the system? How would that payback period compare with, say, golf carts? Sorry if I’m cynical, but I’m old, and occasionally grumpy. Seriously though, looks like they are thinking a bit like me… I have a collaborative posting site for projects like that, but I haven’t really had time to consider management issues, so I haven’t posted the address yet…

Hi Bryan,.. Thanks for the input. First of all, about PRT having always had problems with groups of people… I think there is a reason for that. It is that most PRT is modeled after trains or cars and carries the limitations of that legacy. I am specifically referring to no massively parallel boarding, which allows extremely high traffic volume. No vehicle with wheels on the bottom can do it, because people need to cross the tracks to board. I have seen designs with vehicles coming up out of the floor, or seen stairs coming down, but let’s face it. They are expensive “work-arounds.” This is not a PRT problem. It is a bottom track problem. The other problem that big groups of one way traffic brings is the problem of replacing massive quantities of departing vehicles as fast as they leave. That is a close proximity storage problem. If you look at a train yard, you see the most efficient way to store cars that can’t turn tightly, either up and down or left and right, and it’s not pretty. But dense on-site storage is not a PRT problem but a maneuverability problem. Once dense on site storage is coupled with massively parallel boarding, PRT can match any system out there.

Anonymous,..I guess I mean (by “shuttles”) some form of group transportation that is matched with the limited number of destinations I envision as a first iteration. This whole station thing started with the question of how few stations it would take before other forms of transportation would support a better business model than PRT. How small can a PRT system be and still be the best alternative? Since that was the underlying, original question, it seems reasonable to think in terms of a half dozen stations or less. In that environment, a shuttle for each station could fit in the sim station, and they could load and leave faster. It doesn’t really matter what the nature of the shuttle is. It matters that PRT lost the boarding speed battle, at least for that PRT design coupled with that station design. It is also true, of course, that in a mature system the PRTs could be departing for 90 or more separate destinations, blowing away the shuttle alternative. But right now I’m looking at business models involving very limited PRT systems, so all ideas like shuttles represent real competition.

I am probably going to devote at least one more post to station design and probably a lot of what I want to say has already been said here. I want to give this all a bigger spotlight, however, than I can get on these back pages. I really think that it is worth challenging the orthodoxy on these matters. PRT can’t do stadiums? I want proof. Is no good for hub and spoke? Let’s crunch some numbers. Maybe PRT is more versatile than we give it credit for.

cmfseattle said...

Dan,

- there is a behavioral aspect to this, as Bryan alluded to. your favorite author wrote about it:
The Capacity of a Personal Rapid Transit System. the section on station capacity brings up questions about what assumptions were made in those simulations.

Chris Xithalis has written a freeware PRT simulator (note that it simulates a network using synchronous control, same as ULTra, but very different from the asynchronous point-following control used by taxi2000). you might be able to use it for testing different station configs.

- the ULTra biz model is compelling BECAUSE it's mainly competing with autos (rather than existing transit). part of the payback, in this case, comes from doing things that only their system can do.

akauppi said...

On Dan's last post:

"How small can a PRT system be and still be the best alternative?"

My answer would be: no particular size can be a limit because it varies by each case. What is important is:
- the PRT connection covers "local traffic" completely (= suburb, island, something where people naturally do short distance travel s.a. to the groceries)
- the PRT connection provides feeder service for some longer distance traffic means (s.a. train, metro)

This I would see as a minimum. Islands of PRT communities can grow with this recipe, to be eventually connected and then suddenly changing the city geographics (is that the right word?) by doing so.


One question on Dan's latest:

"I am specifically referring to no massively parallel boarding, which allows extremely high traffic volume. No vehicle with wheels on the bottom can do it, because people need to cross the tracks to board. I have seen designs with vehicles coming up out of the floor, or seen stairs coming down, but let’s face it. They are expensive “work-arounds.” This is not a PRT problem. It is a bottom track problem."

I don't get this. What do you mean by "no vehicle with wheel on the bottom can do it"?

Anonymous said...

Hi,

I would like to stress, that PRT networks DO NOT NEED large stations! All we need is a 5 bay (parallel) stops (cannot call it really stations).

The bottleneck is line capacity and NOT the stops. having a 5 bay stop, which can receive/despatch 700 vehicles p/hour (very achievable case with MISTER) and with only 1,5 persons per vehicle, i.e. 1000 people p/hr - is more than enough. It is so because having a "standard" stop ebery 300 meter and a private stop (hotels, shopping centers, office blocks etc.) gives another 3-5 stops p/km. Therefore you'd have 6-8 stops (6000 to 8000 people) being able to alight or start the journey on each and every kilometer of the guideway system lines. With the line capacity (MISTER case) of 3000 vehicles (4,5K people at 1,5 people p/vehicle) it should be clear that the small stops are more than enough to cater for all the passengers.

The key to the whole PRT network is to ensure that there are plenty of lines, which go along main city streets, e.g. in a grif of 500 to 800 meters. Then you can have a staggering system capacity and thruput p/hour.

Best regards,

Ollie Mikosza
MISTER Ltd.
www.mist-er.com

Anonymous said...

Hi,

I forgot to add, that high capacity PRT systems need subsecond density of vehicles (e.g. 10 m separation at 50 km/h), although it does not apply to the entire network. But vehicles must be able to travel in such close proximity, which is not that hard to achieve ( see how close you cars travel on busy streets or freeways at 50 km/h).

Dan, I also see that you are enslaved by the old transit (tram, bus)idea that PRT stops must be at curb side. This is why you say that serial, narrow PRT stops are better. In case of MISTER, stops will be where they are needed, i.e. mostly inside buildings and on little ground patches, among the buildings. As you noted, MISTER does not require any elevators, as we'll come easily to the ground, if required. This is crucial advantage over any ULTra or Vectus type of solutions.

As for the capacity analysis, you can read it in more detail via this linke on our website. You will see that there is no need to have 12 berth or multilevel PRT stops but only more stops in the vicinity. While 1 metro stop handles 1 km2 area, MISTER would have 30 to 60 stops and would be capable to move more people than metro.

http://www.mist-er.com/mister-description/capability-anaysis.html

best regards - Ollie Mikosza

Dan said...

Hi, Ollie.

I guess the obvious question is this: If you don’t put the stations curbside, how do you get the land? Why would anyone sell you that space, and how would the price you pay affect the cost of the system? Have you considered the cost of entering into all of those negotiations, with all of those private interests, including the costs of surveying and subdividing property, etc.? How can you plan a system without all of these deals having been concluded first?
There are various ways in most countries in which owners may be forced to give up private land for community good, usually for road expansion. I understand that in China the government may simply seize it. In the U.S. these provisions fall under a category of law called “eminent domain.” I have no idea how these things are handled in Poland, but in my country these are very sticky issues, involving lots of money and lawyers. This would be especially true regarding any system other than road expansion. If the system is a “for profit” venture, then you can pretty much give up on help from eminent domain laws. Each station site must be separately negotiated.
An additional problem is that even the publicly owned “easement” is not entirely free for use, as the utility companies may have some say in the matter. On top of that, every street will have it’s share of people who don’t want any kind of change, and they will have very loud voices.
I do not entertain these various models because I think it is how PRT should be, but rather because they possibly represent how PRT must be, to get a foothold. The problem with investors is that they want to invest very little for a very short time to get a huge profit with no risk. The best way to give that to them is to trim a system down to the point were there is maximum simplicity to the system, with minimum cost, yet with a maximum number of paying customers. We call it “Getting more bang for the buck.” It is not a great environment for a concept that should be treated as more of a “public works” project and built as a network, but, unfortunately, that’s the way it is, at least in the U.S.

Ollie Mikosza said...

Hi Dan,

There is some missunderstanding, I think.

I am aware of many land ownership problems in the USA, Poland and elswhere. I agree that PRT will have to be built quickly, simply and be very profitable to get going. For this reason MISTER will have the initial stops alongside the guideway network, i.e. by the curbside - every 300 m. This will be a "standard" system. But because of MISTER's unique guideway switching, which does not require any modification, when the additional stops are added latter - businesses and private land owners will WANT themselves to "provide" small patches of land for the posts and stops in order to have MISTER system to reach their places. And because MISTER will offer its stops at low cost to such venues as hotels, office blocks, schools, hospitals and shopping malls etc., then it will enhance their business.

Therefore I am convinced that there will be no problem with any land issues nor objections from public, as all those city places where stops are needed are already owned by businesses/investors for the purpose of making money. MISTER will enhance their earning power, so why would they not want it?! Especially that it will not cost them a lot, while bringing more people, therefore profits. This is why the cost of land in the cities is so huge - because it draws in people, hence profits.

And for the suburbian connections, we will go on the already publicly owned road (median strips or verges) and bus stop size ground landings. Here and in the city, our 45 degrees guideway climb/descend capability will be also more than handy, as we will "waste" only some 6 m of land before and after stop, which can be utilised for vending machines or waiting shelters.

So in short, while curb side stops are also the initial MISTER configuration, I believe that there will ultimately be more stops owned by private interests, because they will be inexpensive and easily added latter. This is why I said earlier that there will be at least 6 to 8 stops per kilometer of guideways in each direction, because MISTER trunk guideways will always be a 2 way system. Many and small stops, as I advocate, will provide all the necessary pick up/delivery points. People gather at large stops of metro or buses because such transport cannot reach the points where people actualy want to go and it is periodic.

PRT, and MISTER in particular, with its very light and inexpensive guideway and large number of vehicles will be able to reach almost all venues and provide contignous flow of people, thus pre-emptying any congestion, even at peak times.

Ollie

Dan said...

Dan The Blogger Responds-
Ollie, How do you deal will twenty or thirty story buildings at quitting time?

Ollie Mikosza said...

Dan,

by having 10 stops and 4-6 PRT lines in the vicinity. This means some 200-300 people per minute are able to board and leave the area (same a super busy metro station). It means 10-15 min even for the biggest office block, housing 2-4K people.

Discount tickets if 2 people board the same vehicle (they most likely know each other, so there is no personal safety compromised). Such schema may boost capacity by 50-100%.

Ollie

Ken MacLeod said...

Hi Dan and all!

I'm the author of the simulator that created the animation cmfseattle linked to. The source is at prt.sourceforge.net, written in Python.

That animation is running at 3X speed. The tick marks on the clock represent minutes. The simulator is real (i.e. the timing of the rail car doors [dwell], people movements, prt loading, and prt acceleration are as accurate as the information and algorithms I could find). Only the layout of the "transfer station" itself is simplified to visually demonstrate the common question "can PRTs handle a train letting out?"

James Joyce said...

"The necessarily elevated stations, such as is required by the PRT International and Skyweb Express systems, must include an elevator (for the disabled) a feature I have criticized in the past as not being repeatable throughout the suburbs, for cost reasons."

Well you could have a simple stairwell for the able bodied. And wheelchair bound people could use their cellphones to order up a special pod with a bogey that can lower the pod at residential stations. See the below video at 3:30 for a rendering:

https://youtu.be/rtrB82YObXw?list=PL4715F5099DB7CAB6