This famously infamous study was disproved years ago. This study had tones of holes. It even contradicts itself in places. For example it specifically states that the big killer is speed difference and it states, with all things considered states with high average speeds do not have higher fatality rates than states with low average speeds. The authors of this study even admitted that compliance was poor and declining the "safety benefit" seemed to be less noticeable, and fuel savings were insignificant. This study is probably the worst work the Transportation Research Board put out!