3 ms·
Keep in mind that the reason for 55mph speed limits is not about safety so much as it is about energy efficiency (set during the oil crises of the 70s, never ra
by ericd 15y ago
Keep in mind that the reason for 55mph speed limits is not about safety so much as it is about energy efficiency (set during the oil crises of the 70s, never raised again in many places). Going faster increases energy loss due to drag with the cube of the speed, so I don't think we're going to see 200 MPH speed limits until we get something much more energy efficient.
This could make some of the political problems with upping the speed limit that much go away, though.
- leot 15y ago... something like having every car slipstream the car in front of it?
- ericd 15y agoYeah, potentially, but you're not going to reach the efficiency of a train as long as you have individual cars with a bunch of different use cases/designs.
- LockeWatts 15y agoPut the largest one in front?
- ericd 15y agoI never opted to take any courses in aerodynamics, unfortunately, but my understanding is that establishing a laminar flow ( http://en.wikipedia.org/wiki/Laminar_flow http://en.wikipedia.org/wiki/Laminar_flow ) is vital at those kinds of speeds, which requires a surface that the air can flow along smoothly. With a biggest-in-front arrangement, you get some slipstream benefit, but you also get a whole mess of turbulence, and there's no way you're going to rival the speed of a bullet train without a lot more energy spent. You want a mostly smooth/unbroken surface that the air can flow along.
- philwelch 15y ago...and as long as you have 2500 marginal pounds of vehicle per 1-2 passengers.
- suby 15y agoAbsolutely, but even if you go beyond 55 mph, I think that self-driving cars would still be a net benefit in terms of conserving energy. Traffic jams, which are a tremendous waste of energy, would be eliminated if every car was self-driving.