Personal Rapid Transportation

guest post by Todd McKissick

We all can’t wait for High Speed Rail to come to our town. Whether we’re referring to fast traditional trains on wheels (HSR) or those that float down the track on magnetic fields (maglev), this is the 21st Century, so what most people desire is the full featured deal. Anything less is just another compromise. They have been touted now for 40 years that I know of.

But, as usual, it begs the question: is this really the best solution? I’ve found a lot of different solutions and reviewed everyone of them, but only two stand head and shoulders above the rest.

First, let’s look at some of the specifics of what we’re asking for. It runs really fast so there’s lots of possibility of crossing the country in a couple hours. It gets its efficiency mostly from packing lots of cargo into a very efficient vehicle as most trains do. It’s clearly better than getting 25, 60 or 85 passenger-kilometers per liter in a fully loaded airplane, Suburban or Prius. (That’s 65, 140 or 200 passenger-miles per gallon.) As long as it’s comfortable, this is all good stuff.

Unfortunately, to accomplish this, maglev takes a fairly standard sized train and hovers it over a massive rail with thousands of high-powered electromagnets to float this 80+ tonne piece of machinery from one town to another. It accelerates slowly and brakes slowly, unless you want to double the incredible amount of power it uses already. Its rail system consists of hundreds of tons of concrete per 30 meter segment to make the rail and the support beams, and we all know that concrete is horrible for the environment. And lastly, it costs a billion dollars to build each couple miles of the system.

I’m thinking there’s a better way.

To truly combat the automobile, the airplane and other forms of transportation that use lots of fossil fuels, let’s first look at the last mile segment. This is from your door to the store, work or school lobby or even to your friend’s door. Check out this picture from a company called SkyTran.


It’s called Personal Rapid Transit (PRT for short), and it’s courting numerous locations around the world right now. Basically, it’s a small carbon fiber pod that holds two seats and an iPad. This pod hangs from a small rail which then hangs from arms on regular telephone-style poles. At certain locations, a set of steps to a platform is placed to allow people to call for one and hop in. These terminals are cheap enough that they can be placed so that you’re never more than about 2 blocks from one in town or a couple miles in the country. In fact, they can be incorporated into lobbies, shopping malls, schools, sports arenas and even the higher floors of high rises because they are really just a landing to stand on (or ramp for those using wheels). Up to 350 kilogram pallets can be shipped autonomously. The one-way rails pass each other at different elevations so collisions are avoided while off-ramps to terminals simply drop down to a separate rail to stop on. This allows following traffic to continue at full speed while you merge on or off.

Now for the fun stuff. Once you get in and select your destination, it takes you straight to your end destination. Initial speeds are advertised at 70 kilometers per hour (45 mph) for town and 240 km/h (150 mph) for country but the top speed is well over 320 km/h (200 mph). It’s really only limited by wind resistance. This means you can board one at your sidewalk and step directly onto the upper level of a sports stadium 80 miles away in 25 minutes. Need a 2 hour nap before reaching the kids’ house? You’ll have to be farther than 450 kilometers away. When you figure in all the time needed for the various legs required to travel, this is the fastest way to travel any distance between 6 and 600 kilometers. Ya just gotta love avoiding parking at the airport to switch to a plane, because you can get there faster by avoiding the plane altogether—not to mention airport security!

The ride is perfectly smooth and quiet and offers iPad access with wifi support for your own devices. The pods can even be ‘ganged’ for when you have more than two riders (or kids) so that you load your kids in one car, connect it to your car virtually and then follow them to the destination. Along the way, it can switch the order so you can get out first for safety. Each rail has the capacity of a 3-lane freeway. Since the rail is upside down, balancing suspension is not needed because there’s no chance of the pod falling off. In other words, the curves are all banked for the set speed so the passengers feel no side force.

The energy required to operate it is equivalent to getting 85 kilometers per liter (200 mpg) in a loaded car because it is lifting small enough loads to take advantage of ‘passive levitation’. This is a type of maglev that uses drag to levitate the car. This kicks in at about 1 kilometer per hour, raises the car off the wheels, and diminishes to negligible drag once you pass 22 kilometers per hour (14 mph). Coupling this with regenerative braking means that you really only need to provide the energy to push against the wind. In fact a canopy of solar cells over it could power the entire system during rush hour for free. The rail is designed to also incorporate transmission and/or distribution power lines, 3G / WiFi internet connectivity (including backbone and user distribution) and possibly other utility services. A nationwide network installation could reduce US oil imports from 12 mbbl/day to around 3 mbbl, cutting the cost we pay to OPEC from $700B/yr to $175B/yr.

The cost of building such a system is still fairly high at €4.7/km ($10M/mile), but even that’s 1/19th of the cost of most HSR, and it’s and expected to come way down. The cost to the riders for a privately funded system (before profit, of course) is about €0.02/km, or 4 US cents per mile. Compare this to the cost of a personal vehicle which comes in at 14 times more. When you envision the scope this could be implemented, you can see that many targeted communities could do away with roads altogether, and opt for wider bike paths (to accommodate the occasional moving truck) and more nature. Parking lots could be located in cheap real estate areas or eliminated altogether. Delivery trucks could be replaced with individual pallet deliveries directly inside the factory. In short, all deliveries would eliminate the return trip. Cargo sharing could be implemented along with interstate passenger ‘opportunity’ trips for low cost travel for those who can’t afford travel. If there were a public outcry for this system and we decided to install it nationwide, each community could fund a significant chunk of it from existing road funds with no change in taxes. Or private individuals could invest to install it on a for profit basis.

I mapped out my small 12,000 person town, hit all the major points directly and put a terminal within 2 1/2 blocks of every house, for a total price of $160 million. The annual cost to pay it off completely in 10 years would be around $5-6,000 per family before considering the added savings like providing transportation to those in our population that can’t legally drive now. That’s 60% of what people spend on cars today. What better way to help young adults get their lives started without debt? All infrastructure additions can work in parallel with existing roads and utilities and installation time is roughly 2-3 miles of rail per week per crew. You do the math. If there were a global push behind PRT, we could cut our energy dependence, our environmental impact (not to mention the impact on people’s lives) and bring nature back into our communities.

That covers the short range travel but we still have long distance air, rail and international travel to address. Enter Evacuated Tube Transport.


This system suspends a long vacuum tube overhead or under water to guide mini-trains of 6 passengers on extremely high speed, long range trips. By evacuating the entire length of tube, most of the wind drag is removed, allowing it to travel at speeds up to 6,500 kilometers per hour (4,000 mph) with a maximum of 1 g of acceleration in any direction. The ET3 website suggests that intra-state travel will run at around 550 kilometers per hour (allowing for 2.5 kilometer radius u-turns) while the higher speed legs across the country or under the ocean surface can do a loop in a 320 kilometer radius.

A sample trip from L.A. to N.Y. would take 3 minutes to accelerate over the first 160 kilometers, 42 minutes to cruise the middle and 3 more minutes to slow down while capturing the remaining momentum as electrical regeneration.

Of course, riding in a vacuum requires a pod capable of safely withstanding dangerous pressures, but even transoceanic underwater travel poses no problems we don’t already deal with for other causes. It would be worth the ride for just the scenery if there were transparent sides on the tube, but one has to wonder what you could actually see at that speed below sea level. And since a 6 hour trip across the Pacific would not include any stops, there are some obvious human considerations which would need to be dealt with. Even considering these issues, the economics are sound in dollars, resources and energy. As you can see on their page comparing to standard trains, the ET3 system far surpasses even the Skytran for efficient long distance transport. One could only hope for the merger of the two, where you hop in a Skytran car on your corner, zoom straight into a ET3 loading system, jet up to high speed, cross half the globe, reverse the process at some foreign destination and charge $100 on your card, all in a couple hours.

If you think this is is all hype and fairy land, you might want to search around for some of the projects around the world that are reviewing these two little gems. It’s only a lack of popular opinion that’s holding these two back. Let’s make this happen with a little viral support!

21 Responses to Personal Rapid Transportation

  1. Arrow says:

    “If you think this is is all hype and fairy land”

    I am afraid this is exactly how I think about it.

    Especially the EET, the cost of maintaining the vacuum in a giant tube running under ocean is likely to be astronomical. What if an earthquake breaks the tube during operation? That would result in a catastrophe of epic proportions.

    • Arrow says:

      Ops, I meant ETT of course.

      And one more remark, the last year Japan earthquake shifted seabed 24 meters and elevated the coast 3 meters in some places, I don’t see how you could engineer the tube to withstand such events.

    • Todd McKissick says:

      Both maintaining the vacuum and accounting for expansion/contraction/movement are standard engineering skills taught in 2nd year college.

      Tanks and pipelines now regularly withstand >65 bar (900 PSI) for highly explosive natural gas. The leaks that do occur at those pressures during regular maintenance are virtually undetectable. Why should 1 bar be harder? Even 30 meters under water it is a much easier fluid to seal against.

      The real question should be how low of a vacuum is practical to maintain. The cost to pull a vacuum is directly proportional to the volume of the chamber and proportional to the square of the quality of the vacuum. If a better vacuum causes less air resistance, it becomes a simple matter of economics to decide.

      On the expansion issue, the tube would obviously need to include both curves and some allowance for movement on the pole mounts. In a segment crossing the Pacific, it would be easy to accommodate expansions in the kilometers by routing it in a pair of gentle arcing curves. The harder problem might end up being the ocean currents.

  2. Richard Howe says:

    Great ideas! Let’s do it!

  3. grlcowan says:

    There’s always the option of rigging nuclear power plants to make motor fuel rather than electricity.

  4. jefferyhalper says:

    I would love to do my own research on this, and plan to. If even some of it is a real possibility, you (and whoever you can get to help you deal with the politics of it) should shout this from the mountain tops. The airlines, trains and auto manufacturers are all going to punch whatever holes they can find it this. These “other people” that you are going to get to help know all about public opinion and how to fight entrenched industries. We live in Kingman Arizona. How long do you think it will be before we can take the boys (we have two) for a ride?

    • Todd McKissick says:

      I have no affiliation with either one beyond a couple phone calls for information a few years ago. I do try to keep up on their progress though.

      The Skytran, in my opinion, is the most viable to get started quickly. I can easily see a university campus installing an entry level system which quickly expands to include some external major attractions, then bus routes and eventually schools and neighborhoods. Unfortunately, those entrenched industries you refer to have already gotten the first shot off. I was informed 4 years ago that after this was reviewed in Michigan (or Minnesota?), the rail companies successfully lobbied to get the term “rail” legally defined as “steel wheels on steel rails”. I also know that at one time, Masdar and Holland have considered pilot projects. With the economics, I personally think it could be started quicker in some small town that simply puts up their own factory and starts growing it outward.

      I also know of some up-and-coming energy game changers who are grooming their future business models to team up and do this privately.

      The ET3 seems to be following a different funding model. They are selling licenses in trade for technology and solutions to various problems (both technical and political). They project that the interest which China has will be enough added to those partners in another year or two, to get it done.

  5. Hudson Luce says:

    Yeah, it looks pretty much like hype to me, especially the vacuum system – pulling a vacuum and then keeping it going takes a lot of energy. Perhaps if you were to use a pneumatic tube system it might work better – and that’s proven technology, in use for over 100 years – all that takes is compressed air (see http://en.wikipedia.org/wiki/Beach_Pneumatic_Transit and http://en.wikipedia.org/wiki/Pneumatic_tube#Pneumatic_Transportation). Suspension monorails have been in use in Wuppertal, Germany since 1901, and would be ideal for use in the median areas of interstate highways, since grade is less of a consideration than with conventional rail transport – but you’d want cars with 40 people capacity or so (see http://en.wikipedia.org/wiki/Monorail).

    • jefferyhalper says:

      I plan on researching this, but if even part of this is truly possible, please get yourself some people who know how to change public opinion and get to the power brokers of the world so that you can get this stuff moving. The world will certainly be a much better place.

  6. Todd McKissick says:

    Pulling a vacuum is a much easier and less energy intensive problem than pumping air in a tube across the country. Natural gas booster stations dot the countryside to pump that gas down the pipeline. The one near me, that I worked at as a teenager, has 20 engines powering the compressors and each ranges from 1,000-4,000 horsepower. I’ve actually ridden on one of the moving pistons in the 16 cylinder engine. They’re not small but they only get the gas another couple hundred miles down the pipe. A vacuum station could be located at any point on the pipe’s length and only has to remove what is leaking in. If the pipe held pressure out perfectly, it would only need to accommodate what the airlocks let in.

    Regarding the existing monorails and larger capacity cars, I think you miss the point of the savings due to less weight. By having smaller cars, both systems above benefit from a cheap, lightweight rail or tube support structure. If you increased that to 40 passengers, you would need a support every 10 meters and each of them would need lots of concrete/steel. In the Skytran case, even the type of maglev technology will benefit from the lighter cars. It uses passive maglev which requires no levitating power anywhere in the system. That’s not viable with heavier cars (maybe not even the ET3). This is more along the lines of a cable-hung gondola without the limitations of a physical cable.

    One additional benefit on the Skytran system is that by hanging the cars from the rail, they can eliminate all suspension equipment, further reducing the weight being moved around. Gravity is very predictable in it’s direction. Even a monorail needs extra equipment to balance the car from side to side.

    • Arrow says:

      “Pulling a vacuum is a much easier and less energy intensive problem than pumping air in a tube across the country.”

      It all depends what you mean by vacuum. For example reaching outer-space quality vacuum is next to impossible on Earth, even going below 100 nanopascals is a great feat which requires specialized materials and baking of the entire system in high temp before operation.

      So the question is what kind of vacuum is needed for a car to achieve 4000mph without overheating? The webpage linked above has no technical information at all, perhaps one of you is able to do a rough calculation?

      Also while the vacuum certainly lowers drag it also makes cooling much more problematic due to thermal insulation.

      • Todd McKissick says:

        You’re exactly correct that it depends on the quality of the vacuum. As I mentioned to your other comment above, it becomes a simple matter of economics based on how often you want to boost the speed back up to the maximum. The trade-off is wind drag vs. evacuation level. I have no basis for judging this (haven’t done the math yet), but it would seem logical that $1 spent on reducing drag periodically goes further than spending it on propulsion energy for every trip.

        Given that this issue even exists, this means that at speed, there’s plenty of air for contacting a radiator to dissipate heat. Plus, there’s always the option of thermal mass that can be ‘recharged’ between trips.

  7. nad says:

    Todd McKissick said:

    I’ve actually ridden on one of the moving pistons in the 16 cylinder engine.

    Do you have photographies of this? I’d love to see them!

    • Todd McKissick says:

      I wish I did. This was when I was about 18 and working summer jobs to pay for school. The only camera we had then was an old instamatic. The plant is still in operation but most people in town don’t know anyone that works there since Enron went under and ownership changed hands. The bore and stroke were (from memory) 3 ft. x 4 ft. and it ran full speed at 900 RPM. The whole engine was 2 stories tall, about 15 ft. wide and maybe 30 ft. long. We used sledgehammers on the wrenches to turn most of the nuts and bolts!

  8. Giampiero Campa says:

    For what it’s worth, i have lived in Morgantown, VW, for 8 years, and used the local PRT very often.

    It’s not very spread across the town, that is it only connects the main centers, but was very easy to use, convenient, and reliable.

    It’s still working great after basically 40 years …

    • Todd McKissick says:

      While all the existing ones are shining examples that worked out very nicely in the end, they are also examples of how not to save money and resources.

      The Morgantown one has very complex and heavy vehicles. Each of the 4 corners has rubber tires, wheel bearings, brakes, suspension, steering and power driven to it from a transmission from the electrical motor. I’ve heard you can fit almost a hundred people in them so all of this has to be pretty beefy and because of that, the track has almost as much concrete structure as a regular highway. No wonder those systems are all expected to cost $40 million per mile today.

      This does show that even with all that extra hardware, it makes very economical sense. With entry level prices starting at 1/4th of that and then dropping, the Skytran should really take off.

  9. jsn says:

    New York’s first subway was in fact pneumatic: http://en.wikipedia.org/wiki/Beach_Pneumatic_Transit

    It never worked commercially, just a bit ahead of its time.

    • Todd McKissick says:

      Very cool. I didn’t know that.

      It makes me wonder if it might not be better to have stations build up a stored vacuum to various levels and then ‘shoot’ the cars down the track by quickly dumping a calculated amount of ‘vacuum’ in front of it. This would leave a cushion of air in front of the car which could be vented as it approached the end, and then trapped when it should be slowed to a stop.

      But then I remember that we’re in the 21st Century and I’d rather look forward to a system more like what the Tesla car company would build than what Beach did long ago.

  10. Carlos says:

    Sadly, I suspect The Simpsons have forever poisoned public opinion against monorails.

    http://en.wikipedia.org/wiki/Marge_vs._the_Monorail

  11. Tim van Beek says:

    I suppose the most important drawback will be to convince people to give up the association car = freedom.

    BTW: kilometers per hour is usually abbreviated as km/h. At least that’s what’s printed on the tachometers of European cars :-)

    • John Baez says:

      I was the one who translated Todd’s numbers into metric, so I’m to blame for not knowing the standard abbreviation of kilometers per hour used in the automobile world. (Of course I know it in the physics world.) I’ll fix that—thanks!

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