Federal Railroad Administration records reviewed by The Associated Press show there were 10 collisions at the crossing between 1979 and 1997. But no accidents had happened in the past 15 years, the NTSB's Rosekind said.
Six drivers were injured in those accidents. The trains involved were moving slowly at the time, between 15 and 25 mph.
A key question for investigators is whether, after the speed limit was raised, the timing of the crossing gates was changed to give cars and trucks enough time to clear the tracks, Robert Chipkevich, who headed NTSB's rail investigations unit until retiring in 2010, said in an interview.
Investigators will also look at whether traffic lights in town prevented the flatbed truck in front from moving ahead, he said.
Sudip Bose, who was a front-line physician in Iraq, said the aftermath reminded him of a combat triage situation. Veterans instantly tended to the injured, and bystanders helped, too. Shoemaker's husband, Tommy, resuscitated one person and applied a tourniquet to a bleeding woman.
"Instincts kicked in," said Bose, who served in Fallujah and Baghdad and was volunteering at the parade.
Associated Press writers James Beltran, Nomaan Merchant, Danny Robbins and Terry Wallace in Dallas; Angela K. Brown in Fort Worth, Texas; and Joan Lowy in Washington contributed to this report.
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