This comment also made me wonder about the cold-weather usefulness of this sort of device. As I write this, it's -20C outside in the middle of the day. Granted, this sort of weather isn't a problem for much of the world but it's quite common here and affects a nontrivial number of people.

The "inefficiency" of a IC engine gets put to some use in that some the "waste" heat is used to heat the inside of the car, and you don't really get that benefit in an electric car (and any hybrid I've been in ran the combustion engine constantly while the heater was on). This problem has existed in the past with air-cooled engines (old Volkswagens come to mind). At the time, it was common to have a separate heater that burned whatever fuel the vehicle ran on. I'm thinking that the same wouldn't work too well on an electric car -- running an electric heater would probably put a really big dent in your range, and it would be a real bummer to freeze to death on the side of the highway because your car's heater killed the "battery". This would be a problem with any sort of electric car, but probably not an insurmountable one.

Probably more serious than that, though, might be the impact on the function of the engine itself. Most IC engines will run fine in cold weather assuming you can get them started. A common problem is that the car's battery (particularly older ones) can't deliver enough power at low temperature to turn the engine. I am a long way from an expert in the effects of temperature on various battery chemistries, and even less of one on how low temperature would impact the capacitor-like devices described in the article. I do know that it would be a fairly serious end-user problem if your car just wouldn't work on a cold day.

Does anyone have any insight into the temperature sensitivity of this kind of scheme, and how it would stack up versus comparable battery-based technologies?

It sounds like a promising idea, but it would be a non-starter in many places if it doesn't perform well in very cold (or very hot) weather.

Wrong. The SkyTrain in Vancouver is NOT maglev.

MagLev = Magnetic Levitation

Being maglev *implies* the levitation, or "float cushion" as you describe it.

I think you are confusing maglev with linear induction motors
http://en.wikipedia.org/wiki/Linear_motor
which the SkyTrain does use. While these type of motors are often (usually?) used in a maglev system, they are also used for more conventional railed systems like the SkyTrain.

Anectodally - Yes. Why else would they bother? The company is obviously not going to spend trillions of yen building a line that they know will be less profitable than the existing one.

More concretely, an earlier poster provided a link to the math, however I can't seem to find it just now. The point was that eliminating the friction is a very big deal.

I realize you're kidding, but just because they'd be invisible wouldn't make them silent. The air displacement alone would ensure that these trains would make a nontrivial amount of noise. Furthermore, placing pennies on the tracks wouldn't be too effective in flattening them since the train isn't touching the track. That being said, in the highly unlikely event that I'm ever asked for my opinion in the design of these sort of trains, I'll be sure to suggest that they keep "invisibility cloak" off the feature sheet.

The problem in North America is that the vast majority of it lacks the concentrated population centers in fairly close proximity to make this sort of thing even approach economically viable. There are some exceptions to this. In those cases, we're left with:

1. Lack of political will to foot the massive up-front cost for something that won't be completed until someone else's term.

2. Rampant NIMBYism which would make it next to impossible to come up with a viable route through a populated area without getting sued into oblivion.

3. An irrational societal addiction to the automobile despite higher cost and risk to life and limb.

Given enough time, #3 will probably be overcome for one reason or another. #1 might be overcome by some visionary. #2 is a tough one because it either pushes costs even higher, or forces you into a route that is far away from where it's needed. Anything is possible, I suppose.

Basically: I wouldn't hold your breath.