history of terror attacks in their trains, although authorities there are ruling out terrorism. how can they be shower? how do you know they? >> reporter: well, they do have indications that there was an electrical failure of the system before the crash which can affect breaking and can affect deceleration and acceleration in the system. so there's a lot going on other than that that wouldn't indicate that there's kind of terrorist activity. >> so electrical failure. why would that happen? >> well, it is could be because of the fact -- i mean, this system is -- while it's a museum piece, a beautiful pews piece of work, then tire system, but a modern marvel it really isn't. it hasn't been updated for quite some years. it's overstretched. 9 million passengers a day using the system, almost twice what the new york subway has as far as ridership, so it's a very stressed system that's being used 24/7 in ways it wasn't really designed to do so the system is getting old and needs updating. >> critics have been complaining