Back on the thread about cars...

There's already hydrogen-powered cars. The niftiest thing I've seen was a car run on compressed-air - a true zero-tailpipe-emissions car! And everyone knows about battery-powered cars and hybrid-electrics.

But all of these need some kind of intervention from fossil fuels. Let's forget about the plastics and paints that go into them, and just go for the fuel. To produce hydrogen, you need to split water molecules. This takes energy, which must be supplied by a power plant - and until we get nuclear fusion going, most of these will be run by fossil fuels. Compressed-gas (air, LPG, etc) - you need a motor of some kind to do the compressing. Batteries - power station again. So the deal is just to try and get the most efficiency out of the energy. Zero-tailpipe-emissions cars are fine for going around places like LA where local emissions are a real problem, but in general the issue is quantity of fuel per distance. And burning the fuel locally (ie. in the car) is usually more efficient than burning it a long way away in a power station and shipping it over on power lines - this does depend on the engine though.

Engine size. The heavier the car, the more engine you need to get it off the line. My 1.4l Peugeot goes quite acceptably, and my 2l Montego (a few years back now) was stonkingly quick in a straight line (best not mention corners ;-). These aren't particularly small cars - I've a friend who's still driving a Montego from preference, and he's 6 foot 2. Is the average height in the US more than 6 foot 2? If not, why do their cars need to be bigger than a Montego?

SUVs. Three things: engine size, front aspect and tyres. They're heavier, so they need bigger engines, but this is mostly due to the size - a minivan isn't going to be significantly heavier. Front aspect is different - a minivan has a smooth body which makes it more aerodynamically efficient, whereas SUVs are deliberately styled to be slab-sided and so suck much more petrol at cruising speeds. Lastly, tyres - the bigger tyres make a big difference to the rolling resistance. If you're not going off-road, you just don't need big tyres on a car.

I have no arguments with ppl owning SUVs or cars with large engines (such as Kendall's gas-guzzling V6 Jeep - don't try to pretend that's an economy car! :-). But I do have to argue with the belief that they are necessities and there are no other options. In the vast majority of cases, there are plenty of other options - if you want to shift lots of stuff then look at a minivan, or if you're too big for one car's driving position then look at another car. If you face the fact that your nice shiny SUV is a LUXURY, then you have no argument against paying top dollar to drive it.

One minor point - the woman who thinks she's safer in an SUV has been conned by the image. The size and weight of an SUV makes it more difficult to make them rigid, which makes them less safe in an accident - the roof's more likely to collapse if they're rolled, for instance. Buy a Volvo instead.

Graham.