Portland Bureau of Transportation collected $19.86 million in 2017 on a tax that was projected to bring in roughly $16 million.
The Portland Mercury first reported the figures on Friday morning.
Voters approved the 10-cents-a-gallon tax in 2016 that called for dedicating 56 percent of the proceeds to street repair while the remainder is dedicated to safety improvements, including for pedestrians and bicyclists.
"After I spent three years working to establish a new, dedicated source of funding for street repair and traffic safety, it's gratifying to see that the voter-approved gas tax is bringing in even more resources than we expected," says former City Commissioner Steve Novick, who championed the gas tax.
"Hats off to the community advocates, the business leaders, and the voters of Portland who made this possible."