Daniel Stern:

Vehicle emissions regulation is one of the greatest success stories ever to come out of activities involving engineers and governments: the air is vastly cleaner than it was in the bad old days, and it keeps getting cleaner even though many more people are driving many more cars much longer distances. Dieselgate has brought up some seldom-discussed topics such as how—or whether it’s even possible—to adequately and simultaneously control locally-relevant emissions (HC, CO, NOx, particulates) and fuel consumption and its resultant globally-relevant CO2 emissions. That overspanning discussion, though, is hobbled by a lack of good data on exactly what’s coming out of all those tailpipes. It’s not that the data would be hard to come by. For decades, there has been technology to produce mountains of it. The tech has been buried by the EPA and big industry.