For those who are interested, very fast rail has some extremely positive implications about what is possible to solve our environmental problems, such as global warming.
High speed rail is not particular energy efficient - around the same as an airplane, often worse. But unlike a jet liner, a train can run on electricity - something we have the potential to produce renewably in great quantities. 375 mph is still much slower than a 600 mph plane. But when you add in time waiting for gates, waiting for landing strips and so on, total journey time will be comparable to air travel even for 2,000 or 3,000 mile trips. So basically we can replace replace almost all journeys entirely over land with train travel. Most trips over 3,000 miles require crossing some bodies of water anyway. Even for longer trips over land, where journey time will be longer, it won't be that much longer. I mean 4,000 miles is a pretty long trip anyway. Even if it takes a few hours more you are not exactly reversing the transportation revolution that made the planet a smaller place.
Why is this important? Because there is not techical solution to reduce emissions from airplanes a great deal if we continue to fly as much as we currently do. You can run a plane any great distance off a battery. And airplane emissions are not just fossil fuel but water vapor. Water vapor on the land is feedback not a forcing. Basically, over any substantial length of time the lower atmosphere has all the water it will hold. Add extra-water vapor and it is on the ground within a few weeks. Remove water vapor via condensation, and it will be replaced within those same few weeks.
But the upper troposphere and lower stratosphere are extremely dry. Release water vapor up there, and keep releasing it on a daily basis (as planes do) and it creates additional warming. There was actually a tiny measurable drop in global temperature after the massive grounding of planes following 911. Biofuels won't solve this problem. Hydrogen, even derived from renewable electricity would make the problem worse, because water vapor is the main byproduct of burning hydrogen. (Note: again none of this applies to such things on the ground. Water vapor as forcing is a problem specific to aircraft, and I guess spaceships.)