Arizona Gov. Jane Hull last week signed a law restricting tractor-trailers to 65 mph on rural interstates, 10 mph below the speed limit for other vehicles. But whether the new law goes into effect as scheduled July 18 will depend on the results of a state Department of Transportation study.

A provision in the new law allows the Arizona DOT to scrap the lower truck limit if a traffic study determines the lower speed is more dangerous or not necessary. The study, already under way, will examine traffic counts, crash history and how dual speed limits work in other states, according to an article in The Arizona Republic.
Also to be determined is whether trucks will be restricted to the right lane of divided state highways, or the right two lanes of divided highways with three or more lanes in one direction.
The study will also look at whether to allow truckers to change lanes to pass slower traffic. "It would not make sense to prohibit somebody from passing a vehicle," said DOT spokesman Doug Nintzel.