Further investigation of the collision revealed that the impact of the fire truck had failed to overcome the strength of the longitudinal panels and the guard rails. Investigators discovered that despite a bulge of several inches on the longitudinal interior panel, there had been no all-the way through penetration of the passenger compartment whatsoever, no joint separation, and no sharp edges created. Instead, they found the substantial impact stress had been shared over a widespread area along the entire structure of the passenger compartment "box", protecting the occupants as intended by the design.