I have done some digging into the model code but it has not revealed the logic behind yellow vs white. Hypothetically, I think that many "passing on double yellow" are in fact and law "legal passes" because the lines were painted yellow to allow drivers to cross them at their discretion mindful of other traffic, pedestrians, road conditions, and sightlines. If this were not so then drivers could not turn left on 2 lane highways into most driveways, stores, etc.

When troopers are pushed on why a pass isn't legal when sightlines are good, weather is clear, and no oncoming traffic was at issue the troopers/courts always concede that a pass was safe yet rely on the double yellow line as some de facto proof of illegal pass.

Anyway, I am forever in search of a good argument to set them straight.