bridges are designed to move a little, but gertie's movements seem a bit extreme.or some residents, crossing her is lake an adventure. >> it was a thrill. it was like a carnival ride. almost a roller coaster. >> historian and author richard hobbs writes about the tacoma narrows bridge in his book, "catastrophe to triumph." >> people would come out on a windy day when there was extra bounce in the bridge and walk across. the motion could be fairly dramatic. >> but some find that wave like motion harrowing. >> as you drove across the bridge you could look ahead and the car in front of you maybe 100 yards would absolutely disappear as you went down the bottom. it was unnerving to a lot of drivers. many who crossed the bridge swore it would be the last time. >>> and on that windy autumn day in 1940, it is the last time anyone crosses that bridge. >> about 10:00 the bridge began to move in ways it had not moved before. the undulations became higher and the ripples across the bridge were verging on dangerous. >> at 10:15 a.m. one of the bands holding the suspension cable