Good article: http://www.bikede.org/2014/04/07/why-share-the-road-is-gone/

Riding at the right hand edge of a travel lane is an invitation for cars behind to pass. That’s fine. But where a double yellow line also exists, it is very easy for a motorist to interpret the combination of the cyclist at the right hand edge of the lane and the double yellow line separating her lane from the lane of oncoming traffic as an invitation to pass in the travel lane. But on roads where the travel lanes are only 10 or 11 feet, this is a potentially catastrophic misunderstanding. The only way for a motorist to safely pass a cyclist when the travel lane is that narrow is to (at least partially) exit her travel lane (into the lane of oncoming traffic). - See more at: http://www.bikede.org/2014/04/07/why-share-the-road-is-gone/#sthash.o29qkBwZ...