About as well as the rest of the country, with the possible exception of Maryland, where they’re used to decoy people by indicating the turn required by the lane you’re in as opposed to the turn three lanes over you’re actually going to make.

I actually wonder whether google maps / Waze integration would be a worthwhile improvement: self-driving cars are a good ways off but simply signaling the direction which the driver was just told to turn would be nice, and a majority of drivers seem to be using mapping apps these days.