"Evacuated underground tunnels for low drag long distance high speed trips." That's interesting because while I've heard of and thought about the concept of a

"Evacuated underground tunnels for low drag long distance high speed trips." That's interesting because while I've heard of and thought about the concept of a vacuum tube train that could go ridiculously fast, I didn't think of a merely low-pressure tunnel that ordinary cars (with pressurized compartments, anyway) could use in flexible manner. You wouldn't go 15,000 mph, but you could do several hundred pretty easily.