Occurs annually every February 27th. This is a day to remember assholes who have come and gone in your life. Whether you encountered them in traffic or they stayed in your life for a longer period, possibly an asshole disguised as a non-asshole, this is the day we remind ourselves who the assholes are, and remember to avoid them at all costs.
"Hey asshole, just because this day celebrates you, doesn't mean you can cut me off in traffic!"
"Hey look, after not telling me he had a girlfriend and trying to get me, asshole broke up with his girlfriend and now decided to try to get with me. No way. He's an asshole; we remembered him on National Asshole Day."
The lane on a highway directly adjacent to an off ramp lane where Assholes try to cut in at the very last possible second to avoid a line up. This generates new traffic in the asshole lane and a subsequent chain reaction into neighboring lanes.
It is a major root of rush hour traffic on highways worldwide.
Passenger: "Dude get out of this lane quick"
Driver: "Why?"
Passenger: "Because it's the asshole lane!"
Driver: "Thanks you are so wise"