In the Phoenix and Tucson metro areas, motorcycles are required to pass an emissions test as part of the registration process .
Only way to get around this requirement, is to have collector insurance and historic vehicle license plate, vehicle must be at least 25 model years old to qualify for the plate .
The Arizona Department of Environmental Quality, (ADEQ), petitioned the Federal Environmental Protection Agency, (EPA), to waive the requirement for motorcycles to undergo the emissions test in the two largest metro areas of Arizona, as they found out that motorcycles contributed about .007 % of vehicle emissions, the EPA granted the waiver, but it's still lost somewhere in the state governmental 'red tape' .