Wednesday, February 4, 2015

165> Tips for Designing PRT

Recently I have been corresponding with a new PRT developer, and I was struck by how similar his logic is to the many who have come before.  He initiated his communications by saying that the first step to a successful solution should be a fresh look at the problem.  He then stated his list of design criteria, tying back each decision to the problems that it would solve.  Before very long, he had narrowed his design to something very similar to the SMART platform, yet quite different in many important ways, and I found myself defending the specifics of my approach.  I thought I would share.

Design differences don’t just come from differing views on the practicality of one mechanical solution over another, but also from the original assessment of the problem itself.  PRT is the would-be solution to a host of different grievances.  To some, it is primarily an energy/climate saver.  To others the main emphasis is downtown mobility, while some would try to solve the problem of gridlock on our highways.  The various PRT solutions that are out there, it seems to me, are all pretty well crafted for their intended purposes.  What worries me is they stick to their respective missions a little too tightly. 

Current PRT offerings are not versatile enough to harvest sufficient passengers from the varied, real-world cityscapes to be economically viable until they have reached a critical mass of coverage.  The cost to achieve this break-even coverage is simply larger than what cities can afford or, at least, are willing to risk their careers over.  Here is a brief synopsis of the problem:

For PRT (or any other public transportation system) to be a serious contender, it must pass two tests. First, it must not lose money.  Second, it must perform its function better than alternative choices. When PRT can clearly meet these two criteria, it will be adopted, pure and simple.  Starting with the first test, let’s imagine the simplest, cheapest system, a simple loop between two stations.  PRT costs money, and that only gets returned through fares.  The separate costs of track, stations and vehicles must each be amortized though their respective lives and these numbers (along with operating costs) tell us how many passengers need to use those assets daily to make the system break even.  Here’s a hint.  It takes lots and lots of passengers to make the payments!  With two stations, the only people who will use the system are those who need to go to one of those two destinations. While you can buy fewer vehicles, and you can make smaller stations, you can’t reduce the track costs to where only the occasional pod will pay the bills, so that component (the track) bleeds money from the stations and vehicles, leading to its logical elimination.  Now we have another shuttle bus on the streets.

As for the second criteria, such a simple route lends itself better to a larger, scheduled vehicle anyway.  Since everyone is going to the same place, why not ride together?  Even a few stations between would not represent much added inconvenience.
Above is a “heat map” of 5 layouts, representing increasing numbers of loops and stations.  The warmer colors represent greater traffic.  These are not representations of city blocks nor would it ever be possible to have such evenly spaced stations.  Passengers are only where you find them, and then only some of the time.  What is shown, though, is how stations are interdependent for passenger traffic.  Each station is both source of new passengers and a destination for others who would not otherwise ride. In a full-sized system, (not shown) the vast majority would be hot yellows and oranges, and only the outer perimeter would be the unprofitable purple or blue.  PRT clearly can’t start too small.

Needing more closely associated network nodes to be effective is not unique to PRT.  The same heat map and lack of profitability at the outer edges can be seen with a bus system or parcel delivery, for example.  Yet networks are not necessarily all equal when it comes to the ability to grow “from seed.” The key is making each part of the network viable in its own right.  No doubt the builders of the very first stretch of railroad already had a pretty good idea that it would be profitable on its own, and each subsequent branch surely met this test as well.
 
When it comes to priorities for designing the perfect PRT system, this business of needing a whole network from the start is a whopper.  It is the elephant in the room.  Yet with proper design I believe a formula for growth can be found.  There’s more.  Next time you are somewhere that you think would benefit from a PRT system, try identifying the next closest station sites, and estimate how many passengers each such station would attract.  If your experience is anything like mine, you will soon see that good sites are not at all easy to come by, and those with lots of foot traffic are usually on private land or are squeezed by roads that have been widened as far as limited easements will allow. At best they are in patches, separated by areas that don’t need PRT at all.  I pity the poor city planner tasked with finding station sites every half-mile that have enough pedestrian traffic to warrant an elevator equipped station.

The mobility problems faced by the urban and suburban populations differ greatly, and often PRT designers are biased by their own experience.  There are differences due to geography (such as climate) and even city-to-city topographical differences, such as water frontage or hills.  Political differences are important because they effect funding and attitudes toward public works in general. There are even historical differences.  One that I am often reminded of is (then) President Eisenhower’s “cold war” strategy of initiating of the US interstate highway system, resulting in urban neighborhood segmentation and the suburbanization of an entire nation.  Now, 1 out of 4 miles driven in the US is on an interstate, often at maddeningly slow speeds! The point is that these are among the factors that individualize a city’s needs, even as the economics of starting a PRT company push toward a more “cookie cutter” approach, and therein lies the rub.

This is where “SMART” comes in.  “Suspended Multi-axis Automated Rail Transport” is not a PRT system per se, but a development platform.  Any system that can move vehicles in 3D can also work in 2D.  Any system that can travel at 90 mph can also travel at 30.  If it can turn in a 6’ radius, it can certainly manage any street corner.  The idea to avoid “baking in” needless limitations.  The SMART vehicles are very capable and full featured because someday they might be expected to be that way. After all, people will eventually want, from PRT, the same qualities they would expect from a manually driven taxi service, and investors, equally, will prefer a fast, efficient and comfortable fleet to maximize returns.  In the meantime, there are tough choices in store.  SMART, with all of its “bells and whistles” is, admittedly, an extremely (if not prohibitively) expensive way to start.  Yet its basic architecture, especially the track, addresses the above problems squarely by being uniquely versatile.   
With PRT requiring a whole network to operate profitably, and with the vast differences between different cityscapes, the problems that predicate a PRT designer’s job are immense and varied.  Some examples include how to put dirt-cheap stations everywhere and anywhere; how to take the shortest route between lucrative sites instead of being detoured by worried landowners; how to piggy-back other services, like carrying utilities or street lighting; How to give local planners more and better options; How to get property owners to allow stations on their parking lots and in their lease spaces; How to attract the most riders without cutting fares, how to encourage night traffic and freight, how to minimize operating costs, and so forth.  

Why PRT has not entered the mainstream is not simply a matter of suspended vs. supported design, linear vs. rotary motors, or third rail vs. battery power.  It is the big structural issues regarding network size, versatility, and the business model, and translating these overarching issues that into physical form should be “job one” for the PRT designer. 

20 comments:

kaidoloor said...

To provide for more versatility, I suggest we need a stationless capability, where people can go onto and exit pods 'at their doorstep', without this blocking other pods moving. Remember the Metcalfe's law of network utility: the mode stops PRT can make the more useful it is. As the suspended rail will be suspended with columns I have dreampt that these columns can be used for the pod to 'crawl down', but I cannot envisage a technical solution for this. I hope you can.

Lee Sprecker said...

The concept of having a POD lower itself to ground level seems doable but there are problems. In a ‘suspended’ system the ‘bogie’ is ‘traped’ within the track. If the POD was lowered what happens to the bogie? If someone requests a POD and it is lowered to them how long would the customer have to wait for it. Is the POD lowered from an of-line track or on-line? If off-line then we have two tracks again. If one track then that track is dead while the POD is being lowered or raised. At the bottom there would need to be some type of enclosure to prevent the POD from being lowered on top of someone. There would need to be a place to pay for the trip. Having empty bogies running around the system seems to be a confusing mess. No the problem to solve is not just how to lower and raise PODs but all of the associated problems. I do not think that lowering and raising PODs is a viable answer. Lets work on more possible answers.

Dan said...

Dan the Blogger now knows that Google now sends his “comment alerts” to his spam file, and so will know to check there periodically, so as to respond more promptly to his many insightful readers!

I’m a big fan, Kaidoloor! I have my doubts about “to the door” for PRT, but I believe PRT pickup could resemble a bus stop more than a full station, and there could be more of them, because of their reduced cost.

You might use my little Google search box to check out Posts 150 and 131. The upshot is that PRT can, indeed, climb straight up, and this involves very little extra machinery, other than being able to rotate the vehicle on the swing arm. Post 131 details how to “switch to low gear” with no transmission.

P.S. Thanks for posting and connecting a name to the “Network Effect.”

Dan said...

Lee, I no longer share your worry about lowering pods down onto someone by mistake. I used to, but there are just too many easy ways to solve the problem with today’s dirt cheap sensors and microprocessors. This represents the most basic, elementary entrĂ©e into the field of artificial intelligence. Low cost enables massive redundancy and that multiplies the reliability factor exponentially. There is already a “tilt switch,” on each vehicle, we have talked about weight sensors, and that is AFTER contact, which would not happen in the first place, since there are many ways for the pod and/or landing platform to “see.” In a world where autonomous, self-driving cars are navigating the streets, I can’t see throwing in the towel on such an important feature. NOT A PROBLEM!

I do not see how any of the “associated problems” you refer to amount to anything significant either. The off-line/in line and empty pod problems you mention exist with ALL station designs equally, at ground level or with elevated stations. A payment kiosk need not be bigger than a tablet computer and can be mounted anywhere, and can run off of the track power. You will note that on the picture in post 150, it is on the track itself. Pods might well be left hanging, to avoid vandalism, but it would only take a few seconds to descend…They would go very slow from head-level down, so say, 45 seconds? Beats walking to the next station!

One more thought about the in-line or off-line issue. It is possible (actually it’s more of a certainty) that some locations will not warrant offline stations. In such a case 3 or 4 low volume stations could share a single off-line track. This is not substantively different from a street with driveways. Sure, someone might have to wait a second to pull out, but this would be unlikely and it is better than not having access at all. It is actually analogous to the saw-tooth station design of MISTER or ULTra, just spread out to cover more area. I maintain that finding cheap ways to bump ridership should be the main focus of PRT development, and that the “low hanging fruit” is between the stations with better potential, since the track is passing by anyway. This is not a resource that we can afford to forego!

Lee Sprecker said...

I do see the advantages that would result in having POD/elevator units. On those residential streets where the usage is low we might use on-line stations but they are still ‘stations’ and spacing of those probably not less than ¼ mile apart. To be able to lower the pod at each pole would place a ‘station’ every 90 feet or less. If this can be proven, then it might be the way to get PRT accepted in residential areas, which is essential for PRT success. Just as industrial equipment is equipped with a loud beeper, that is engaged when the unit is backing up, a similar idea could allow safe lowering of PODs (NO PARKING in landing zones). If functional in commercial areas this might be a way to deliver people almost to the door of a business. Here you would need to provide an off-line delivery so at not interfere with the busy main line but in a business or industrial area the ‘extra’ track would probably not be a problem. This would acomplish the PRT dream of taking people from their door to the door of their destination.
Well it does sound like you have convinced me that this is an idea worth trying. With the ability to make payments from your phone it would seem possible for a person in their home to use an app to request a POD and pay for it on their phone. They would enter the number of the post closest to their home and a POD would be dispatched to that pole. OK that will work. What about pranksters who order PODs to many posts? How do we insure that the requester is a real customer? Need to solve that one.
So now just how much complexity and cost does this add to the cost of a POD? I think that every POD would have to be equipped for this procedure or it would be very complex to try to get an ‘equipped’ POD to a person at a shopping center who wanted to get off at their ‘pole’.
I suppose this could be used to deliver packages. The recipient is contacted to set a time to meet the POD then the package could be sent by PODmail. A more likely application would be deliveries to small businesses to a pole near or at their store.
OK so lets get a committee to begin the design of this system. I remember one suspended system cartoon (well it’s not a real movie of a real thing is it!) showing the POD ‘climbing’ down a post and another one showing the POD being lowered on cables. Have these ‘dreamers’ actually designed a working model or is it like my ideas, all in my head and on paper?
Lee

Lee Sprecker said...

Part1 (This was too long)
Now that the concept of lowering the POD to the ground has been stuck into my head I cannot stop thinking about it. The first PRT designs had a ‘guideway’ like a small lightweight elevated highway. But there is no way that you are going to get a Vectus type of guideway into residential neighborhoods. For a PRT system to succeed it MUST be able to get ‘stations’ very close to most of the homes in the area that it serves. So there goes my big idea too.
Then I looked at the ‘suspended’ systems and felt that the (relatively) small ‘guideway’ might be accepted in residential neighborhoods. But there still was the problem of stations. The stations in residential areas could be fairly small but every one would require an elevator and stairs, which adds a great deal of cost to the station and blocks the view 24/7.
Now the concept of just lowering the POD to the ground comes along and that may be the final item that will allow a PRT system to succeed. I do not know which would cost more, elevators and stairs in residential stations plus the station cost or this mechanism on every POD.
So the next problem is just how will this work? I have thought a great deal about that. I am sure that my idea will not be the ‘final’ design but I offer it as a starting point for others to improve upon.
First there is no way that I can see for the support arm to disconnect from the bogie and ‘magically’ ‘latch onto’ the support pole. So another method would seem to be best. That idea is lowering the POD by cables. There would need to be at least two so the POD would not swing around like a flag in the wind. The cables should attach to the sides of the POD perhaps with an upside down ‘Y’ connection to prevent ‘rocking’ on the trip down and up. This then would support my thought that two bogies, front and back should support the POD. Each bogie would have a hoist on it to raise and lower the POD. I remember having a ‘hoist’ in my garage years ago to lift items up to the second floor. Yes it was a big garage. I think that hoist was rated at 1 ton or 2000 lbs. So two 1 ton hoists would have no problem lowering and lifting a fully loaded 2000-lb POD. I do not have any idea at this time just how the POD is released from the bogie support arm and reattached, so this is another problem to be solved before this idea can work.

Lee Sprecker said...

Part 2
Next there needs to be some way to keep the pod from swinging toward and away from the pole. My thought here is to apply the same technology that many ‘waste management’ companies use. The truck has an arm that reaches out and with sensors finds the trash, oops that is waste, can, grabs it, lifts it and empties it into the truck. A similar device, without the lifting requirement, could be mounted on the front or rear of the POD to ‘grab’ the support pole. There could be wheels on the inside of the ‘grab’ arm to allow contact and support while the POD was being lowered and raised. This would provide side-to-side stability while the two cables provide the front-to-back stability. This ‘arm’ should not be under the POD where it would not allow the POD to reach the ground level. This arm would also need to be toward the front or rear so the pole does not block the exit door.
OK so now we have the POD at ground level. How do we handle the wheelchair entry and exit? Well my idea here is that inside or outside of the door is a small platform flips down to the ground when the door is opened. This would also provide a ramp at the stations. The ramp lifts and the door closes or if it is on the outside it lifts after the door closes. I think that the ramp inside is best as there it and its mechanism are protected from the elements.
While I was pondering this concept I was reviewing a report by a committee in Cincinnati, Ohio about possibly installing a PRT system some years back. They eventually rejected the idea for numerous reasons but one that struck me was the need for a method of removing passengers in case a POD is ‘stuck’ on the line. They were going to require walkways from where a POD exited the main track to the station and from the station to the merge point and possibly all along the ‘guideway’. What a cost that would be! For ‘suspended’ systems I just do not see how this would be possible.
Well the two activities collided. If we can ‘lower’ a pod to exit and enter passengers then we can do it anywhere in case of emergency. That should satisfy that one concern that the committee had. With auxiliary battery power if the POD was movable it could be moved to the nearest post and lowered. If it cannot be moved then the pod could be lowered and ground personnel instructed to ‘catch’ it as it gets to them to prevent side-to-side swinging. Another feather in the cap of ‘suspended’ systems.
I am an ‘electronics’ person so I have no idea exactly how to make this work but you ‘mechanical’ people do (notice how I did not exclude female mechanical designers here), so how about getting to work on some actual suggestions?
Lee

Anonymous said...

There is an additional isssue to consider. At some point of time, the pods need to able to crawl up the walls. This solves the parking problem and serves multi-storey buildings. The same mechanics could be used to lower the pod by the supporting columns/piles.

Kaido

Dan said...

OK,.. Lee first – One other concept that you may not have seen was one proposed by SwedeTrack. They used to have about 30 pages detailing their very well thought-out system (Flyway) but the site was very antiquated, using pre-90s (pixelated) graphics, and they have taken it down. They used a combination of an upside down scissor lift and cables. The scissor part could be light and compact since it was only used to stabilize. You should also appreciate the advantages of triangulating the cables instead of having them all parallel, which further helps stability. This system enabled passenger pick-up and drop-off anywhere there was a track overhead. Nothing I have proposed forecloses such an option, but I would note that the system works best with big pods on low tracks, features that many would find unappealing.

What you seem to gloss over, though, is the lesson I tried to impart in this post, as summarized by the last paragraph. (Not to mention the whole discussion around the “heat map.”) Specifically, how are you ever going to pay for the track with the revenue stream from a residential street? You really need to run some numbers. Luckily, I think you are dead wrong about this being required for PRT to be adopted, or I would have thrown in the towel years ago.

As for the business about stalled pods. I think this issue needs to be seen in context of the times. When PRT was first proposed, about a half century ago, the whole system had to be centrally controlled. If something broke, the whole system came to a halt, stranding everybody. As time has progressed, control has been moving steadily toward the vehicles themselves starting first with zone controllers, which, if one went out, would only potentially strand the vehicles in that zone. In just the past few years, however, computers and communications have gotten so cheap that every vehicle can instantly know and share everything, and so full control can move all of the way to the vehicles themselves. As I am working on standards, not systems for immediate deployment, I am content to say that the easiest way to solve the stalled vehicle problem is (or will be) to make each vehicle capable of towing or pushing, either with or without help from support staff. Nevertheless, I have toyed with various emergency evacuation solutions, and I would note that ones that can both lift and lower are much more expensive and complex than “one-time” lowering solutions, which I prefer, as they would be principally for rare, catastrophic events, like earthquakes, where multiple track breaks occur. Of course the best solution is prevention, and these days sensors can detect many problems before they get out of hand. Still pods should roll into the shop periodically, for a complete physical!

Dan said...

Kaido, about the wall climbing… As I mentioned, the SMART system uses simple “cog” technology to allow vehicles to climb at any angle, including straight up, although buildings should have elevator capacity of their own to match their occupancy so it should not be necessary to supplement it with an external, vertical PRT track. The general dimensions I advocate allow a track to pass between floors of any typical building. Following up on my remarks to Lee about suburban pickup, as well as your comment about Metcalf’s Law, I would reiterate that each new loop that gets added to a system needs to be financially self-supporting. There are certainly times when a proposed loop may pass through a residential area and being able pickup reasonably near to those residences should, I believe, be part of the system design. If I were to make a rule of thumb, I suppose it would be that any potential loop to be added should serve at least two new main destinations and the rest should at least be on streets that are important enough to support a bus route. Otherwise, Metcalf or not, it will just be an obvious money pit and never get funded. The “baby bear” track could go further from the "beaten track" by quite a bit, being so much cheaper, and it would be visually less objectionable, but I have yet to figure out a good business model to exploit this fact. (I must say though, that the idea of speedy little 30 lb. runabouts that can squeeze between PRT pods to deliver stuff to pick-up points has its appeal… Lee scoffed at pizza delivery, but you have to wonder about the absurdity of using a human, a 4000 lb. machine, a quart of gas, and a stop-and-go road network to do what a 10 lb. delivery droid could do… and you don’t even need to tip!

Miko said...

I think you overstate how extensive a minimal PRT network would have to be. A single linear route with several stations along the way could be very useful in many situations. That's basically what the Morgantown PRT is.

Consider, for example, the idea of adding a PRT line to an existing subway, or even creating pods that can travel on existing lines. Take a look at the Washington DC Metrorail map. I rode the yellow line for years from its furthest station out. I can definitely say that just being able to travel directly to L'Enfant Plaza without stopping along the way would have made my mornings better.

Dan said...

Dan the Blogger responds;
Hello, Miko... Welcome back!

From what I understand, everyone involved in the Morgantown system totally lost their shirts and got out of the business, even if it has been highly successful as transportation in the aftermath.

As far as your experience with the yellow line is concerned, it is hard to generalize from that. I have, in past posts, pointed out that in the right circumstances even a single loop could be viable. Crossing a body of water alone may itself be enough, as I pointed out in post 156 (about bridges). Certainly joining an existing network with 70 (Metro) destinations bumps up the heat map by more than a few degrees! I have also suggested that terminating a system at a Park & Ride would be a way to bring people to the “cold” outer edge of the network. An airport or a tourist destination might serve a similar role.

Also, do not underestimate the ability of an older transit system to have shaped a city around itself. Areas become important destinations, over the years, simply because they are within walking distance of mass transit. Your neighborhood, and therefore your use of Metro, may even be partially the result of the yellow line itself. (Or not…) Anyway, existing transit creates a great pool of pedestrians who are potential PRT customers, and these folks are not around otherwise. (And let's not forget that your yellow line commute was actually 9 loops...just flattened into a two-way track.)

I have gotten similar views from people in other cities around the world with extensive transit systems, and have come to believe this effect is largely responsible for our differing opinions on these matters. Of course designing anything has to involve acknowledging and planning for worst case scenarios, and one would want a PRT system to be able to be expandable into areas that are currently highly automobile dependent, so I will generally “stick to my guns.” After all, wouldn’t it be great if Ultra, for example, were to be as ideal for the surrounding neighborhoods and for commuting to downtown London as it is for the Airport itself? My dream is for a system that can (and will) grow city-wide, in a way that is replicative across the globe.

You are right, though, in noting that I probably made PRT seem like a poorer solution than it actually is in many, many places. I should probably try to voice these design concerns in way that does not cast a negative light on PRT generally. I will keep this in mind for future posts!

Dan said...
This comment has been removed by the author.
Miko said...

Actually, I don't think we're really disagreeing that much, if at all. Like software and other technical projects, PRT needs to be implemented in small steps... a "smallest useful change" approach. I'm just pointing out that there are some pretty small useful changes out there.

The Morgantown PRT was funded by the federal government. It did indeed have all the signs of being an over-budget, over-schedule waste of taxpayer dollars. Unexpectedly, however, it turned out to be a pretty solid design and now 40 years later it's still popular. It's too bad that our country didn't learn from some expensive mistakes instead of writing the whole thing off as a bad idea.

There's no doubt that transit options affect the development of a geographic area. Intentionally planning on those changes is called transit oriented development and it's quite a hot topic in municipal planning right now. The Ithaca PRT study discussed TOD at length. Your idea of a PRT system out to a park and ride is perfect example of TOD.

Lee Sprecker said...

I wish that people would stop calling the Morgantown system a PRT. It is not ‘personal’. It is not ‘rapid’. It is transit. So Morgantown is a ‘Transit’ system similar to the busses that run around many large university campuses without charging the students a fare. The same goes for the ULTRA system at Heathrow Airport. This is again not ‘personal’. It is not ‘rapid’. It is ‘transit’. This is a number of electronically guided glorified golf carts on a dedicated guideway. The Vectus system research in Sweden has resulted in a motor driven ‘transit’ system, now called ‘SkyCube’ in South Korea, that takes people from an entry point into a delicate environmental area so people can see (sort of) how things look when man does not destroy them. It is the equivalent of the monorail at Disney World. It is a ‘free’ ride that runs on a dedicated track between two points. It is NOT PRT! To hold these systems up and say ‘look PRT works’ is bad. This gives a totally wrong idea of what a PRT system could do. People see it as an amusement park ride. Is that all we are ever going to see?
None of these systems charges a fare so there is no way to determine if they would pay for themselves by demand. I doubt that they would. To my knowledge there is and never has been a system that meets the general description of a PRT. There has never been a ‘demonstration’ system with over 10 off-line stations, multiple ‘loops’ with paying customers to demonstrate that such a system will support itself that has run for over a year to prove reliability. Until that happens there is little chance that any governmental entity will commit to allowing someone to put a system in their area of responsibility.
Until those, who will have to endorse a system, see that what is being presented has been proven to meet all regulations that will apply, no deal! Until they see that they will be able to purchase replacement parts from multiple sources for competitive bidding, no deal! If everything is ‘proprietary’, no deal! Until they see reliable third party figures about the cost of installing and maintaining a system, no deal! Until they see figures that prove that the system will in fact pay for its installation, maintenance and operating costs, no deal!

Lee Sprecker said...

Part 2
None of those things have happened and none will until those who want to see some form of PRT developed get together and develop some ‘standards’ which most likely will not be their idea for a standard but something in between what they want and something others want. Then those interested can design their system to meet those standards in their own ‘proprietary’ way. However those who would allow a system to be installed would know that it is not a totally ‘proprietary’ system, that they will be able to maintain the system with materials from builders other than the original builder and those items will work on their system seamlessly. Businesses can purchase a railroad car from many sources, which are made for special loads, but those cars will all meet the ‘standards’ set for cars to be used on railroads, maximum length, maximum width, maximum height, maximum weight, break system, coupler system etc. Standards did not destroy creativity it allowed the industry and many companies to exist and flourish and even have ‘proprietary’ design items.
Dan you say that the reason for developing your blog was to begin the process of developing standards. Well you have been going on and on and on about various things sense 2008 but as far as I can tell have not proposed one standard! Perhaps you are worried that if you propose a standard others will come along, show problems with it and another standard would emerge but it would not be Dans’ standard. Come on Dan propose one standard! Perhaps that a POD must not weigh more than 2000 pounds fully loaded. Let those who contribute to your blog pick that ‘standard’ apart with valid arguments until there are no more complaints and a ‘standard will be born!’
The subject of PRT has been talked to death. Perhaps in reality this is true. I find less and less interest in the subject on the Internet sense about 2005. Dans’ blog just perpetuates that by talking about it but not really trying to get something going that will make it a reality. Everybody talks about the weather (PRT) but nobody does anything about it. Talk is cheap, especially on the Internet.

Miko said...

Lee: Let's take it down a notch. Dan's blog and ideas are some of the best innovations I've seen toward bringing open source PRT designs to reality.

I think a major reason there's more talk than doing is because most of us don't have enough money for the doing. Speaking personally, I'd love to devote myself to designing and building PRT innovations, but I have to work a job and pay the bills.

Dan said...

Dan the Blogger Responds –
Miko, a couple of topics you have raised outside of this post deserve a public answer, so let me get to them first. You mentioned that my Table of Contents has many dead links… This is true, and I have fixed a couple, but it will take a while… I’m pretty busy these days. Also, yes, I would encourage you and others to read and comment on older posts. Blogs have a nasty habit of burying the good stuff early on. Many people do, indeed, read these long after the fact, and I am alerted to any new comments via email. You probably won’t get an immediate response though, as the readership back there is low enough that it is not exactly my highest priority. I am also preparing to go back to the woods soon, so I’ll be “off the grid” most of the time.

Your talk of Municipal Planning just made me sigh. In Houston we have no zoning and take the very busiest, most congested areas of the city and build and build with absolutely no regard to the traffic these developments are causing. I frequently have to go down one thousand ft. stretch that takes 6 or 7 minutes, to get on the (just widened to 10 lanes plus feeders) stop-and-go freeway, and yet they have at least 150 stories of new construction going up within a half-mile. We have a bit of light rail, but it is downtown, five miles away. Of course Texans are not exactly known for believing in government planning or control! (And we wonder why we can’t meet federal clean air guidelines…) Anyway, as you can see I introduced my latest post by revisiting some of what you were talking about. There clearly are places in many, if not most, cities where even one or two loops would be useful.

Dan said...

Lee, much of the reason that there seems to be so little activity in this field in the last few years is because progress is no longer just in our hands. PRT is rapidly becoming just another application of robotics, communications and industrial automation control, so it’s like perfecting tube TVs when flat-screens are just around the corner. Any next-gen PRT system will be made almost entirely from off-the-shelf building blocks that thousands are learning about in colleges every day. Cities will have no problem finding people capable of understanding and maintaining the system, as was my worry when I wrote that sidebar back in ’08. That leaves matters like track details, which, as you know, I have been working on.
Setting standards as you suggest requires some kind of quorum of people who are reasonably qualified and informed on the issues at hand. Back in ’08 I had high hopes that the blog would “go-viral” and attract numerous engineers. Never happened. Somewhat later I added file sharing and a Wiki. These are the real tools to do what you suggest, because with a Wiki, pages pertaining to certain subjects don’t ever get buried, so if you don’t have enough input at a given time, at least over months or years more people can weigh in. The file sharing allows version-numbered modifications to prints and so forth. Nobody, however, has ever shown any interest. If you want to start it up with a first page, be my guest!
Standards, ideally, force minimal compromise…We “standardize” that clockwise turning tightens things because it will work just as well as counterclockwise every time. As systems get more complex, however, less people are likely to find a standard beneficial and more are likely to find it problematic. A standard is, after all, a limitation. For this reason I believe that we should be extremely judicious in their use. I don’t want to dictate to cities what they need or to PRT companies what their business model should be. I believe the one-size-fits-all approach has had as much to do with PRT’s lack of implementation as anything else.
When I started, nobody had really investigated the upper limits of what suspended PRT could be capable of, and who would ever want to “standardize-in” features that would keep it from reaching its full potential? Therefore the logical first step was all about breaking limits, rather than setting them in stone. It is one thing to establish goals, ranges, guidelines and assumptions to move the design process forward; that is always necessary. These are best solidified cautiously, however, because with every final rule, you set up a “butterfly effect,” that can create unforeseen ripple effects far downstream that are impossible to fix. Standards for interoperability, good. Standards to guide the design process, Bad.

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