[Severian]

The fact that one high-caliber bullet can shut down a multi-billion dollar transport system is all that needs to be said.

It's a silly idea and is best made on the Moon or Mars where atmospheric pressure is already low enough to not cause catastrophic failure.

[bigbubba]

Incidentally, regular trains getting shot at in America is not uncommon. Apparently Boeing has to check fuselages shipped by rail for bullet holes, because that happens..