When I was a kid, I loved to "ride shotgun," and pay attention to how traffic worked. (Back in my early days, cars didn't even have seat belts, let alone airbags! I depended totally on Dad or Mom to safely get me to Point B.)
As I observed and listened, I came to understand that the "dashed" line meant passing was allowed, and a solid line meant passing was not allowed. Of course, I understood there's always some risk when you cross that line, no matter what the line looks like, because it puts you out there with oncoming traffic.
(You may deal with oncoming bicycle traffic no matter which lane you're in, since they choose not to enforce those confusing laws on bike riders, who are obviously incompetent. But I digress.)
Early on in my marriage, I got an expensive education on the double-yellow line.
I was driving on Highway 21 between Lowman and Idaho City. For those not familiar, it's about 35 miles of serpentine 2-lane road, winding through lush forests and over mountain passes. Mostly it's double-yellow line, and a lot of it is 35mph or less. I wasn't passing anybody... but I crossed the double yellow line with the left wheels of the car. Maybe a foot over. (Who HASN'T done the same thing at some point between Lowman and Idaho City? I bet nobody!)
Darn the luck - a state patrolman was coming from the opposite direction. He saw my tires over the line. (Don't misunderstand - it's not like there was a near-miss between he and me or anything... I was totally back in my lane 200 yards before we passed.) He must've been bored, or in a bad mood, because he turned around, pulled me over, and gave me a ticket!
I was so sure that the double-yellow line meant "no passing," that I contested it. Which meant a weekday drive up to Idaho City, where the court house is located. Despite my passion, and my declaration that probably NOBODY has driven between those two points without drifting over the line, the law was clear... you cannot cross that line, period. (The judge had enough pity that he at least minimized the fine.)
The double-yellow line should mean "compromised sight distance - cross with extreme caution." As currently written, it is one of the sore points with the new "safe passing" statute designed to protect cyclists. A motorist might have to follow a bicycle for a considerable distance, if there's a double-yellow line... even if there's plenty of sight distance for a driver with decent judgment and depth perception to successfully complete the maneuver. (For the record, I see car wheels cross that double-yellow line in just such maneuvers ALL THE TIME! And I'm fully in support of their being able to do that, from the legal standpoint, as long as they aren't putting themselves or others at risk.)
Passing a cyclist is just one example. Farm equipment, crawling down the road? Letter carrier on a rural route? Police officer and somebody pulled over? (There's a new law about giving the cop plenty of room. But the only legal way to do that would be to stop and wait, if you otherwise have to cross the double-yellow.)
The written statute should be brought into compliance with real-world practices. And I understand that "my" senator - Elliot Werk - will introduce such a measure in this year's legislative session. I hope it gets some traction.
(This situation may be unique to Idaho... or there may be a similar situation in the other 49 states.)