Coming from Central Europe where toll booths are not a thing: I thought it should maybe read "reduced infant mortality to numbers in cities/countries without toll booths" ...
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.
Colorado isn't even in the EZ Pass network.
edit: Correcting myself here, it's EZ-Pass-only at certain times of day: http://66expresslanes.org/e-zpass/default.asp which I find even more confusing.
I thought it should maybe read "reduced infant
mortality to numbers in cities/countries without
toll booths"
Check the paper; it's very readable. Alternatively, know the following:
The reason they chose their approach was because it gives them a "natural experiment" - by comparing the exact same area before and after EZPass, you get a fairly valid experiment with only a minimal number of variables to wrangle.