According to the Associated Press, the study concluded that differing speed limits for passenger cars and trucks would create even more unsafe conditions than having them travel at the same speed.
The study was required by a legislative bill that initially sought to limit big trucks to 65 mph on the rural stretches of Interstates 8, 10, 15, 17, 19 and 40. It also would have limited trucks to the right-hand lane. The bill was later amended to let the results of an ADOT study mandate the ultimate speed.
The speed limit for all vehicles will remain 65 mph on all Arizona state highways and 55 mph on urban freeways, unless otherwise posted.