Sunday, April 12, 2009

PRT - The Myth That Keeps on Missing.

Engineers want it because it's a technocratic challenge.

Investors want it because it promises to make them lots and lots of profits (at whose expense?).

Who else wants it?

Pedestrians? No need!

Motorists? They already have their infrastructure.

Bicyclists? Hah!

Go to Cyberspace Dream for the full story.


  1. A Transportation Enthusiast12:27 PM

    Perhaps you didn't notice that "Cyberspace Dream" is anonymously written, unpublished, and posted on a pro-light-rail website underwritten by corporate entities who have strong financial ties to light rail transit - the big transit industry that would be most threatened by a paradigm shift to PRT!

    So I give you rock solid data, research, ongoing efforts by multiple respected entities around the globe... and you counter with a single unpublished propaganda piece posted on a lobbyist website sponsored by companies like "Tran Systems".

    Incidentally, that cyberspace dreams essay has been debunked *multiple times*. See this, and this (PDF) and this.

    If you want an example of how that paper uses creative math to twist reality, here is a direct quote from that piece:

    "This implies a minimum safe design headway of 16 seconds, and thus about 1/16th the line-throughput capacity claimed."

    They have apparently done their math and claim that no system could possibly operate safely at less than 16 second separation. But one problem: the claim is *demonstrably* false!

    In the 1970s Cabintaxi ran continuous tests at 2 second separation for over a year without interruption. Cabintaxi had regulatory approval to carry passengers.

    Today, there are two separate systems, Vectus PRT and ULTra PRT, which have received regulartory approval at THREE seconds headway, and are doing further testing with the goal of approval at separations as low as ONE second.

    So how does this mesh with Cyberspace Dream's math? They claim confidently that separations less than 16 seconds are impossible, and here we have at least 3 systems that have been extensively tested and approved at LESS THAN ONE QUARTER that, with further reductions pending.

    Of course, Light Rail Now will not correct that obviously wrong claim, because it kills the whole thrust of their argument and makes a mockery of their so-called analysis. So they just leave the misinformation out there in the hopes that people will believe it at face value.

    But now you know the truth: the entire thrust of Cyberspace Dream piece is based on provably false assumptions. There are other examples (see the rebuttals), but this particular one is striking because it's so obviously false. If it were true, and sub-16 second separations *were* impossible, then the regulatory agencies in Sweden, UK and Germany have all approved "impossible" systems. :-)

    If you would like to discuss any other particular claims in the LRN piece, let me know. I've read it back and forth and I am fully prepared to debunk nearly every point. WITH data (I know how much Jean likes data.. :-))

  2. This gets to real crux of the matter. Venture capital and ROI. It drives everything in technological advancement. It has everything to do with money and nothing whatsoever to do with "improving society."

    Even the engineers are driven by capital in these types of scenarios. It means jobs. Money for research, patents and patents translate into more money.

    Want to do something positive for transportation in this country? Expand the passenger rail system!

    But no, the government is getting ready to spend billions on stealth warships while the venture capitalists push ridiculous ideas like pod cars.

  3. Yes, I did notice it is anonymous, just as these posts from Transportation Enthusiast are anonymous.

    What industry is Transportation enthusiast beholden to?

  4. It is impossible to have a debate about PRT, since PRT, as proposed, does not exist and has never been built. Engineering studies are barely worth the paper they are printed on, not worth the trees destroyed to make the paper. Engineering studies are speculation until put into the real world.

    The F-22 is a marvellously engineered aircraft that has no purpose in the modern world.

    PRT may or may not be marvellously engineered. We won't know until one is built. It certainly has no place in a world of declining oil resources, climate change and changing human perception about life styles and transportation.

    Arguing about separation times in an experimental system on a test track is worse than arguing about how many angels can dance on the head of a pin. There really is such thing as the head of a pin.

  5. A Transportation Enthusiast8:51 PM

    -- "PRT may or may not be marvellously engineered. We won't know until one is built."

    Well, you're right on that point, one isn't being built - *TWO* are. See Heathrow and Masdar, both of which are due to open their pilot implementations this fall.

    -- "It certainly has no place in a world of declining oil resources"

    PRT doesn't need oil. It needs electricity by any means available. In Masdar, it will be solar and wind. And the electricity it uses is less per passenger than any other mechanized transit system conceived to date.

    Now, you can imagine a world where there is NO mechanized transportation whatsoever, but is that realistic? You can *wish* for a world that collapses under the weight of current unsustainable transport solutions, but is that really what you want, to see society collapse?

    So unless you crave societal collapse, or you envision a world where billions of people voluntarily decide to give up their lifestyles, then mechanized transport will be part of our future, and if so, then it might as well be the most sustainable mode. PRT is that mode.

  6. Heathrow is a people mover in an airport moving people from their cars to the terminal. Period. It is not a mass transportation system in a living community with fifty stations to move 50,000 people around fifteen square miles.

    Check your sources, Masdar is not being built. Masdar is not scheduled to be built for ten years! Masdar is a piece of paper.

    Everything needs oil. Where do the plastics come from to build the pod cars? How are the materials for the pod cars and the pod cars themselves transported to the desert to be assembled? Solar transport planes? Sailing ships? How do the people get to Masdar? How does food get to Masdar?


    We are past the point where we have the capacity to build an entire new city in the desert and expect to make a living community out of it. We don't have energy alternatives to oil that can provide the same amount of energy we use now, let alone enough energy to build shining new cities in the desert.

    It's not necessary to crave societal collapse. The world we live in now is unsustainable. Inventing new technologies that add more to our energy demands and waste burdens will not invent us into the future.

    The future is less, not more.

  7. Jean Brocklebank9:24 PM

    What energy source is going to be used to build the sloar array at Masdar to build all PRT infrastructure? Solar electric manufacture of the components or electricity produced by burning oil or coal or natural gas??

    How will all the components for the solar array be transported to Masdar? Electric vehicles?

    How will the materials that make the components be mined? Solar electricity? Are there going to be solar electric backhoes and cranes?

    Last question: please define "sustainable."

  8. A Transportation Enthusiast10:05 PM


    Re Masdar construction: there are 4 phases of construction and the first phase will open this August. Last I heard (a few months ago) they are on schedule for that opening.


    This phase will feature a small starter network. Construction will continue and the network will gradually expand as the city is built out.

    Rome wasn't built in a day. ;-)

  9. A Transportation Enthusiast10:37 PM


    My understanding is that they are taking construction energy very seriously and have incorporated it into their zero-carbon goal. Now, of course there has to be a bootstrap where perhaps the initial phases rely on power from carbon-emitting plants in Abu Dhabi, but my understanding is that they will offset this by feeding back into the Abu Dhabi grid as the solar grids are constructed. So perhaps there will be a time when they are in carbon debt, but they fully intend to "repay" that debt by pumping an equivalent amount of solar energy back to Abu Dhabi over time.

    I don't know about mining operations, but as for carbon emissions in construction vehicles (which will likely NOT be purely electric), I believe I read that they intend to plant trees to negate the construction carbon footprint.

    So as I said, they are taking construction energy VERY seriously and are taking efforts to ensure that the construction phase is as carbon neutral as possible given current technology.

    "sustainable" - in simplest terms, a process that is capable of operating indefinitely. This implies that no finite resources will be consumed, and no destructive waste products will be produced. Solar power is sustainable because it consumes what is essentially an infinite resource. Water power is sustainable as long as the lakes don't dry up.

    For transportation systems, sustainability would (at the very least) require a sustainable energy source. This basically disqualifies EVERYTHING in existence today: cars rely on finite oil and emit destructive gases; electric-powered transport *usually* relies on unsustainable grid power so it should also be considered unsustainable. This would include PRT, at least in the short term.

    However, the grid can be made more sustainable over time, as sustainable surces of energy such as wind and solar are added to the grid. Most PRT systems would fall into this category - not truly sustainable today but may become more sustainable over time as the grid sustainability improves. Some PRT systems also propose solar panels on the guideways, which would replace potentially unsustainable grid power with locally generated solar, pushing those systems closer to overall sustainability.

    In any case, PRT's extremely low power requirement makes it *more* sustainable than any other form of transportation even if it's fully operating on an unsustainable grid.

    I also think of sustainability in financial terms. Financial sustainability means an entity supports itself indefinitely with no loss. Trains and buses are not financially sustainable because they always require subsidy (even NYC heavily subsidizes its transit). PRT has the *potential* to be financially sustainable even accounting for construction costs.

  10. Podcars work fine. The problem are the concrete salesmen who want to hitch a ride.

    Podcars need a green line to follow, I dunno why everyone thinks podcars need their own lane or skyway, they work quite well on normal roads and they mix quite well with pedestrians.