[RedDevil]

Originally Posted by Frank Lee

Aerohead has mentioned in the distant past about a device to aid boxy things- like semi-trailers- that consists of a quarter round length mounted such that it stands proud of the front surface and flush with the sides/top. It traps a "stagnant" bubble in front while promoting ordered flow past it to the sides/top.

All indications are that these types of "A" pillars are basically doing the same. Of course since they are angled back on the cars it's not so much a stagnant bubble as the bulk of the air mass is going up and over, but I suspect there are "stagnant" or probably more like sliding zones along the fronts inner to the pillars and the flow to the sides is orderly.

Exactly. The trapped, or slightly thicker than usual layer of 'slow' air if you will, also makes the hood to windshield transition more smooth, and maybe that's why you see this feature more and more pronounced with the boxier new cars, as their windshield is steeper.
When the edges are wider at the bottom that would have the same effect as if the windshield were tilted slightly more horizontally.

Another plus is that the A pillar can be thicker and stronger this way without impairing vision.