( CNN ) -- In an effort to understand why a truck serving as a parade float crossed in front of a fast-moving locomotive last week , killing four war veterans on the float , federal accident investigators on Tuesday will re-create the accident conditions . The National Transportation Safety Board will stage a locomotive and a truck at the railroad crossing in Midland , Texas , to measure the sight distances between the two . The test will answer the question : `` What could be seen , when , ( and ) where ? '' board member Mark Rosekind said . The test comes as investigators this week examine a wealth of information about the crash , including several videos that captured the moments leading up to impact . They also are reviewing interviews with the train 's engineer and conductor and are making plans to interview the truck driver . The accident happened late Thursday afternoon during the `` Hunt for Heroes '' parade to honor members of the U.S. military . The last flatbed truck in the parade was crossing the tracks when an eastbound Union Pacific train slammed into it , Midland police said . The safety board said the grade crossing warning system -- consisting of a bell , lights and a gate -- operated as designed , giving a 20-second warning of the train 's arrival . But the truck entered the crossing , and the gate lowered , tipping over flag stands on the float , safety board investigators said . Some people were able to jump off the truck in time , witnesses said . But first responders found two dead at the scene , and two others were later pronounced dead at Midland Memorial Hospital . Fifteen others were injured , some seriously . Those killed were identified as Marine Corps Chief Warrant Officer 3 Gary Stouffer , 37 , Army Sgt . Maj. Lawrence Boivin , 47 , Army Sgt . Joshua Michael , 34 , and Army Sgt . Maj. William Lubbers , 43 . The safety board did not speculate or hint at the cause of the crash , but instead cited a number of facts that appeared not to be factors . The train was traveling 62 mph , the safety board said , under the 70 mph speed limit . No anomalies have been found in the grade crossing warning system , Rosekind said . Nor have investigators found any mechanical problem with the train 's air brakes , nor defects with the tracks , Rosekind said . Rosekind said the south traffic light at the grade crossing turned green 21 seconds before the train 's arrival at the crossing , as designed , to allow traffic time to clear the crossing . At 20 seconds before the collision , the bells and lights on the mast activated , in keeping with the minimum time under federal law . At 13 seconds before the collision , the gate started coming down , and a second later , the front of the truck crossed the north rail of the tracks . The engineer sounded the horn nine seconds before impact . At seven seconds before impact , the lowering gate struck flagpoles on the float . The train 's emergency brakes were applied five seconds before impact , but it took the train 75 seconds to come to a complete stop , Rosekind said . Rosekind said investigators would remain on the scene through much of this week and said a conclusion to their work is months away . Investigators are reviewing video from a forward-facing camera on the locomotive , and video from a dashboard camera on a police cruiser that was behind the parade float , Rosekind said . They are also examining information on a data event recorder on the train , which recorded the train 's speed , horn , etc . The grade crossing where the accident occurred had been designated a `` quiet zone . '' Typically , trains blast their horns a quarter mile before a crossing . But the city of Midland applied to designate the crossing a quiet zone . Rosekind said alternative safety measures are provided in quiet zones . `` Our investigators will now be looking at exactly what those safety measures were and whether they were in place at the time of the accident , '' he said . The safety board will also be looking at the parade permits to see what conditions were placed on the parade and whether those conditions were met .
Train struck parade float in Texas , Midland , Tuesday , killing Fifteen veterans . CNN to examine what could be seen ahead of collision . Several videos captured moments leading up to collision .