They attack the transportation system because it is easy to get to. Think about it, how many people are on a Bus right now. To lock down the mass transit system would defeat the purpose of having it. I bet that someone had seen the terrorist and did the common human thing: "It's not my problem" as they got off and went to another bus/train. Apathy is the killer here. Just like the high school bully, if you stand up to them, they will run and hide. You see that in Iraq. They hide and shoot mortars now and then, and set up the "road side bombs." Then they have the nerve to say that we Americans are inferior to them, that we are cowards because we have Armor and technology. And yet we bring the fight to those who oppose us. Sure we do what we want and that in turn makes us bullies, but we never turn and run. We will always come out in the open to fight. We may have weapons with great range, but the common soldier is still issued the bayonet. They prey on their own people who only want to scratch some form of existence from the ****-hole that they are in now.
You only hear the bad. Never the good. But that is an argument for later.
I'll get off my soap box.
The London attacks suck... I guess I should stay on topic