> The back half of winter was characterized by blackened, salt-saturated puddles and banks. I wonder if the prevalence of EVs has made things less dirty in the winter.

The dominant cause of that is probably brake and tire particulate matter, not car exhaust. And EVs make tire pollution go up (because they're heavier) and brake pollution... I'm not sure if the weight effect there is counteracted by the decreased amount of friction brake use (as opposed to resistance braking).

On my Polestar 2, I was surprised how in actual use, friction braking was basically zero - to the point where when you start a trip the brakes are used for a few seconds to make sure they're still working (and scrub them a bit.) In actual driving - without trying particularly on my part - it's just always regen.