Meanwhile, the relatively cheap addition of glow-in-the-dark strips along the stairs after 1993 made the evacuation much easier, survivors reported. But many thousands of people did not even know where the stairs were. Fewer than half the survivors had ever entered the stairwells before, the NIST report found. Only 45 percent of 445 Trade Center workers interviewed after 9/11 had known the buildings even had three stairwells, according to the early results of a study conducted at Columbia University.
