The pedestrian walkway that collapsed Thursday in Miami, killing at least six people, was being built using a popular but relatively new bridge technology specifically designed to speed construction while maintaining safety. It took only six hours on Saturday to install the 174-foot pedestrian walkway, part of the 320-foot-long FIU-Sweetwater University City Bridge project at Florida International University, which had been scheduled for completion early next year. The project was to have included 9,900 feet of event space that didn't cross the roadway.