joining me now via skype from connecticut, steven flynn, the author of the book "the edge of disasterlding a resilient nation." are these bridges dangerous to travel on right now? what's going on? >> well, they're not dangerous under normal circumstances here, but they're a warning sign. should be a big blinking red light that we as a country have inherited a bunch of infrastructure and we haven't been keeping it up very well, never mind upgrading it for the kinds of needs we have going forward. >> you believe that ignoring these huge infrastructure problems we have here all across the united states could hurt our national security. what do you mean by that? >> really the last president who got that infrastructure as a key national security issue was dwight d. eisenhower. we've been struggling ever since and making the appropriate investment. so one is of course that it's the underpinning of any advance of society. it's economy relies on the infrastructure. but more importantly post-september 11th when we see terrorism is directed at civil targets, whether we saw in boston, where i am

sorry state of the bridges and roads we all rely on, we're joined by northeastern university's steven flynnco-director of the research institute for homeland security. you saw him in dan's report. he's also the author of "the edge of disaster, rebuilding a resilient nation." first explain to us what these terms mean, structurally deficient and functionally obsolete, because according to the federal highway administration, there are 66,000 bridges in the united states right now that are structurally deficient. >> what they basically mean, the bridges are worn out. they are in a condition that they are in danger of failing at some point if major repairs aren't made. they're not an imminent danger. if that were the case we would be shutting them down but they're old and they need to be repaired or replaced. >> earlier today, the chairwoman of the national transportation safety board told me that you can have a bridge that's older but still be very healthy. do you agree with that? >> it's true, yes, if it's very well maintained. but when you look at one in nine of our bridges in the entire coun