The most interesting thing here isn't really comparing having tolls vs not having tolls (although if you live near toll booths that would be interesting, I supp

The most interesting thing here isn't really comparing having tolls vs not having tolls (although if you live near toll booths that would be interesting, I suppose). It's having a way to directly see the health effects after a change that reduces local exposure to emissions from cars idling in a given location. There has been other research that shows a correlation between certain health outcomes and proximity to highways, but there may be confounding factors in that type of study, whereas this is almost more like an interventional study even though the change obviously wasn't actually made for the purposes of the study. This is very strong evidence that many of the negative health effects that have been shown to be correlated with proximity to highways are indeed caused by car emissions.