Saturday, February 19, 2011
As many of you know, I have never been a big fan of dual mode. The problem is simple. If a vehicle is light enough to be part of an effective elevated PRT system, it is too light to be a robust road vehicle. Conversely, if it is sturdy and comfortable enough to not seem ridiculous as a car, it would require a track that would be unacceptably massive and costly. You tend to either have a bad car or bad PRT or both. Yet if you thread the needle just right, they are off by tantalizingly little . Lithium based batteries, ever-shrinking computing power, carbon fiber technologies and miracle plastics are nudging things forward, but what is needed is something really dramatic. Something to knock off half of the weight form the start.
The other day I was thinking about all of this, or at least how to transport people that last mile. I was considering bicycles, scooters, and Segways, and wishing for something that would have a roof to keep the rain out. I was even considering what technology would be involved in matching PRT to a Segway, instead of the other way around. I even have a picture to prove it.
It was around then that I decided to do an image search for a rain-proof Segway, and I stumbled onto something that had passed beneath my radar when I first heard about it. It is the EN-V concept car, which, as it turns out, which may well be the “best-yet” dual mode platform. It is a joint venture between GM and Segway, and it does two things that really reduce the weight problem. First of all, it runs on two wheels instead of four. Roadworthy tires and wheels are heavy, after all, especially if you include durable shocks and springs. This vehicle also lacks a mechanical steering wheel and all associated linkages. Like the ULTra, it is self-navigating, or at least, “drive by wire.” That brings up the intriguing notion of having the vehicle drive itself back to the station after dropping off a passenger. The side-by-side, two-wheel arrangement enables steering without any pivot assembly, and also allows 360 degree rotation in place, something that might add considerable flexibility in station design.
The relationship between the EN-V and PRT seems symbiotic: PRT can’t go the “last mile”, and the EN-V can’t go all that far. The EN-V’s shortcomings in speed and battery life could be rectified by an electrified track. Equally promising is that the EN-V weighs in at under 500 kg, and that is for a version with a much bigger battery and motor than would be required for dual mode use. Also, as long-time readers well know, I have my doubts about how good of a PRT vehicle can be designed and constructed by any fledgling company without seriously deep pockets for R&D. GM and Segway have dumped a lot of money and knowhow into this project. They have based the vehicle on what they call the “Puma” platform, which is literally just that… a versatile, self-balancing platform slung between two wheels.
I really think this combination deserves some serious consideration, more than I have time for within the context of a single post. Look forward, therefore, to more on this subject in days to come.
Here are some related videos: This short clip shows the “Puma” platform without the passenger compartment.
This second video shows a bare-bones version in action as well as a simulation of a city street designed for using the vehicle as an ULTra-like PRT.
The EN-V comes in three flavors, as shown in action in these vids.
Saturday, February 5, 2011
Well, we’re having a snow day in Houston…Well not really a snow day, actually it is an ice day. The buses are not running. Everyone is being advised to stay home. At the moment, all of the freeways are closed. It seems like a good moment to curl up with a warm laptop, and tap out some thoughts about this epic winter.
Being a mere six hours from Mexico, we are not well prepared for these kinds of weather events. We have no salt trucks or snowplows, but yesterday a truck preemptively applying a deicing solution caused a great traffic jamb, of which I was a part. It did no good.
It boggles the mind to think of the calamity that these weather systems are causing across the US (and Europe?) this year. In the last one, there were even fatalities in New York because ambulances couldn’t make it through. Enough, already! Is this really the best we can do?
The ongoing recession should serve as a “teachable moment” that illustrates the effects of a few percentage points of reduced economic activity. Clearly, these weather events must work against our collective well-being, event though we may not make the association. Such shutdowns further compound the wasted productivity caused by simple traffic, illustrated in the chart below.
Being paralyzed like this should point out the consequences of having all of our transportation “eggs in one basket.” For example, the rise of radical Islam makes me wonder if anyone has really considered what would be the effect of a sustained campaign of sabotage against road-based travel in a modern society. After all, a single disabled vehicle can nearly freeze a whole highway. Imagine the effect of terrorists simply targeting the tires of moving vehicles on a continuing basis… or even traffic lights for that matter. (I’m glad my readership is a very small and constructive group, or I would not share such notions)
There is also the warm weather counterpart to the “snow day,” which is street flooding. PRT systems can be specifically designed with this in mind. As ridiculous as it sounds, many urban areas around the world are built on floodplains. What would have been, for example, the result of a PRT system in New Orleans? If predictions of climate scientists are correct, we are in for lots of major weather events of all types in years ahead.
Anyway, my point is that society has reached a point of unprecedented interdependency, and is very vulnerable to any disruption in travel. These are not the days when everyone had canned leftovers from their large gardens and a cord of firewood on hand. If our transportation stops, our means of survival (and escape) does too.
Astute reader Lars Endre recently referred to raised PRT as exploiting “the virgin third dimension.” I love the phrase. It occurs to me, however, that it is not really virgin at all, at least around here. Here we have lots of spaghetti-like highway interchanges that are many stories tall. The interesting thing is that these forays into that third dimension are the very reason this city has drawn to a halt. Raised roadways and overpasses freeze first. We have many miles of raised HOV (High Occupancy Vehicle) lanes, connected to “Park and Ride” parking lots. Our embryonic light rail system continues to work, but nobody can get to the stations.
Too bad we can’t exploit the nice dry undersides that such elevated structures enjoy. Oh wait… We can! Yes, it’s the underside of that virgin third dimension that offers the possibility of completely weatherproof transportation. (You knew I would turn this into a shameless plug for suspended PRT sooner or later, right?)
While we're talking about snow, although this is a bit off-topic, I would like to take this opportunity to mention the troublesome act of repeatedly salting roads. It reminds me of the age-old notion of dumping waste into the ocean or atmosphere because “It’s just so darn big that it can’t be hurt.” We know better now, but we continue to salt the earth on a mega-industrial scale. (10 million tons per year in the US, which works out to 66 lbs. annually per person) It works its way downward, eventually, to the water table, where it migrates “away.” Some readers may have seen these structures along roadways and not known what they are. They are structures for storing all of that road salt. I only wish PRT could solve this dilemma too.
Finally I just thought I would share these pics that I happened upon. As you can see, the need to remove snow from our 2D transportation systems is not confined to just roadways.
Well it’s a day later and the sun is shining and the roads are clear once again. Time for me to wrap this up…
PRT cannot mean an end to roads or the costs of maintaining them. There still will be the need to move heavy loads, that last mile problem, and the whole countryside beyond. But an extensive, all-weather PRT network could, in times of crisis, be a very important backup system to have. We sure could have used it yesterday.