Three government agencies continue to investigate the tour bus crash that killed 14 people and injured the other 16 passengers Saturday morning. The National Transportation Safety Board is leading the investigation, with help from the Federal Motor Coach Safety Administration and the Arkansas State Police. But a former chairman of the N-T-S-B is worried that other regulatory agencies won't heed the call for seat belts and other safety measures. Jim Burnett of Clinton, who headed the safety board from 1982 to 1988, said the crash needs to have a -- quote -- "tombstone effect" -- to convince other regulators to take action. The agency has recommended seat belts on buses in the past, but another agency in charge of regulating motor coaches has decided not to implement the requirements. He said the most remarkable thing from Saturday's crash is how the roof tore off as it tumbled over an embankment. He also said there appears to be a disproportionate number of accidents involving buses traveling to and from gambling casinos. He said that is worth investigating more closely as well.