NTSB Investigator-in-Charge Jennifer Morrison shows the Board reenactment animation of collision between tractor-trailer truck and bus in Davis, Okla., on September 26, 2014. Photo: NTSB As a result of its investigation of a truck crash that killed four college athletes last year , the National Transportation Safety Board issued recommendations on Nov. 17 aimed at helping motor carriers address “impairing substances” that are not tested for under federal regulations.
