Rochester is one of two areas nationwide where carbon dioxide emissions from cars decreased over the last few decades.

That's according to A New York Times report that drew on data from Boston University and the Oak Ridge National Laboratory. The researchers looked at carbon dioxide emissions from traffic in 100 metro areas from 1990 through 2017. Of those metros, only Rochester and San Jose, California, showed decreases in both total carbon dioxide emissions and carbon dioxide emissions per person.

Arian Horbovetz, who writes about urbanism and transit in upstate New York, said there's not a clear reason why Rochester would be so different from other cities. He said it's especially strange that Rochester is so different from other upstate metro areas in the report, like Syracuse and Buffalo.

"To say it's puzzling is putting it mildly," Horbovetz said.

Martin Schooping, a program manager in RIT's Golisano Institute for Sustainability, said no immediate comprehensive explanation came to mind for him, either.

One possibility might be that people in the Rochester area are using newer cars and trucks that run cleaner than older models, and that visible charging stations are encouraging drivers to use electric vehicles, Schooping said. But he cautioned that he did not have data at hand for those points.

Schooping also said that traffic tends to flow smoother in Rochester than in many other cities, which leads to better fuel efficiency.

Whatever the explanation, Horbovetz and Schooping both said local governments should invest in figuring it out.

"I think we need to find the root of it, because I think if we can tell that story here, there's some data to be shared with other cities," Horbovetz said.

Brett Dahlberg is the health reporter at WXXI News.