The national speed limit in the United States was reduced to 55 mph in 1974. Proponents and critics of this legislation have looked at the number of...

The national speed limit in the United States was reduced to 55 mph in 1974. Proponents and critics of this legislation have looked at the number of traffic fatalities on major U.S. highways (e.g., I-90, I-65, I-75) for the years preceding and following this legislation. Sonny examined the traffic fatalities on each of the major U.S. highways for every year from 1968 to 2005. Sonny used a: