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I think one must be careful about the train versus car efficiency argument. Trains, for example, are big. You get a dining car, aisles to walk around in, lots of extra space that you don't get in a car--and that needs to be carried around with the people.

Let me turn this into a point that actually carries weight (because, carrying empty space, cost nothing). Indeed it is true that while on a modern train with average filling (40-50%), you have roughly 1 ton for 1 passenger, while for a car (a car not a SUV), you have that when just the driver sits in it.

However, mass is the main factor only when you accelerate. At constant speed, friction is the factor, and trains rule. But even acceleration doesn't really make them worse. On one hand, trains typically gain speed/brake with much lower accelerations (no 100 km/h in ten seconds). On the other hand, modern electric trains (especially those using a lower-than-grid-frequency separate railway AC system, say the 16.7 Hz in Germanic and Scandinavian countries) have regenerative electric brakes, and send much of the braking energy back to the catenary - which can have a greater efficiency than even hybrid cars that recharge themselves while braking. (There are also experiments with adding gyros to diesels for similar short-term energy conservation.)

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Mon Feb 6th, 2006 at 03:04:24 PM EST
[ Parent ]
trains typically gain speed/brake with much lower accelerations

Sorry about that, of course that is irrelevant - the energy input is the same. However, there is a further pointof how often acceleration/deceleration takes place - with street lights and tunrs at corners, I think cars are ahead even if trains have many stops.

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Mon Feb 6th, 2006 at 03:08:21 PM EST
[ Parent ]

Yes. The main killer for cars, even on highway driving, is the frequency of acceleration. Trains have very smooth acceleration/deceleration profiles, which makes them easy to optimize. When they don't, something has generally gone very wrong.

With cars... Well, think about how you drive on the highway. Your speed's usually about the speed limit. Sometimes you drift a little higher, sometimes a little lower. Sometimes you make really sharp changes in speed, like when you come over that hill and see Granny McBloggs putting along at a positively mind-boggling 50 km/h, and again when you pull out to try and pass her. It's better than city driving, but it's still pretty nasty compared to a good train system.

by Egarwaen on Mon Feb 6th, 2006 at 04:01:02 PM EST
[ Parent ]
With cars... Well, think about how you drive on the highway.

I know this is a rhetorical "you", but let it be noted that I don't drive a car :-)

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Mon Feb 6th, 2006 at 04:25:23 PM EST
[ Parent ]

How one drives on the highway. Happy?

I don't either, though I do know how to drive. So I do sort of know what I'm talking about when I talk about relying on public transportation. ;)

by Egarwaen on Mon Feb 6th, 2006 at 04:54:03 PM EST
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