An added measure of safety, on the state's aging deck truss bridges. Wisconsin has fourteen bridges similar in design to the ill-fated I-35 bridge in the Twin Cities. Starting today, they'll be fitted with strain gauge sensors. Wisconsin D-O-T bridge engineer Finn Hubbard says degree of stretching is acceptable, but the extra caution is due in part to the advanced age of all the deck truss bridges in the Badger state: between 50 and 80 years old. The sensors will remain in place for three months, and round the clock data will be analyzed to determine their safety.