Was talking earlier to a homeland security expert. He said, unsurprisingly, that securing mass transit is basically impossible. There are too many access points and too many fast-moving passengers, carrying too much stuff. It doesn’t have the natural choke-points of commercial aviation. He said that DHS has done some pilot programs 1) screening passengers; 2) screening carry-on bags and passengers; 3) screening checked bags (the bags under a train). It all worked, but once you move beyond one train or one station it begins to get prohibitively expensive and complex. So there is not a lot that can be done, but he also thinks that we are “over-leveraged” on aviation (for understandable reasons) and there should be more focus on other vulnerabilities.