Trevor Baggiore, deputy director of air quality with Arizona Department of Environmental Quality, said motorcycles make up 3.5 percent of vehicles on Valley roads and account for less than one percent of total emissions.
"Most people especially here in Arizona in the summer don't drive their motorcycles," Baggiore said. "Also, just the emissions characteristics of a motorcycle are different from cars and they get better gas mileage."
He said dropping mandatory tests will not impact air quality.
The U.S. Environmental Protection Agency supports the change and the requirement could disappear in early spring.