MIDLAND, Texas — Cheered on by a flag-waving crowd, a parade float filled with wounded veterans and their spouses was inching across a railroad track when the crossing gates began to lower and a freight train that seemed to come out of nowhere was suddenly bearing down on them, its horn blaring.

Some of those seated on the float jumped off in wide-eyed terror just moments before the train — traveling at more than 60 miles per hour — crashed into the flatbed truck with a low whoosh and a thunderous crack.