"imagine the chaos it would cause if a suicide bomber detonated a bomb on a train in the tube.[..] That would have devastating effects on the economy (both loc

"imagine the chaos it would cause if a suicide bomber detonated a bomb on a train in the tube.[..] That would have devastating effects on the economy (both locally and nationally)" A bomb of the sort that would fit into a backpack would probably disable the car the bomber was riding it, kill people immediately near the bomber, injure folks farther away in the car, and do pretty much minimal-to-no damage to the tracks or tunnel. In the worst case, the affected tunnel would be out of commission for a few days/couple of weeks while the tracks were cleared and everything would get back to normal. http://en.wikipedia.org/wiki/7_July_2005_London_bombings#Transport_and_telecoms_disruption http://en.wikipedia.org/wiki/7_July_2005_London_bombings#Tra... (keep in mind that US trains have higher crashworthiness standards the European trains, meaning they are structurally stronger)