Few bad-driving sins elicit so much rage from other drivers as driving too slow in the passing lane, a.k.a. the "fast lane." A Far Side cartoon once depicted different rooms in hell, labeled "Murderers", "Robbers", and "People Who Drove Too Slow In The Fast Lane."

As a former fast-lane drifter, I can tell you exactly why people do this, and how to stop it, and why most people's loud statements attempting to "fix" the problem are completely useless.

I grew up in Denmark, where legal driving starts at 18, but I left before I was 18 to go to college in the U.S. I ended up graduating college and moving to Seattle to work at my first job, all without ever having acquired a driving license.

So I learned from a local driving school.

My driving instructor never happened to tell me the unwritten rule of speeding, which was: "If the speed limit is 45 miles per hour or lower, you can usually exceed it by up to 5 miles per hour; if the speed limit is 50 or higher, you can exceed it by up to 9 miles per hour." And he also never told me the actual legal rule for the left-most lane, which is: you have to be actively passing in the left-most lane, or else, move to the right. I suspect that, for legal reasons, most driving schools do not teach the "unwritten rules of speeding" to their students, but most teenagers probably learn them from their parents.

So, yes, I ended up getting my license without knowing these rules, but that's not really the problem. Lots of people end up getting their licenses with gaps in their driving knowledge. The problem was that every time I heard about the left-lane rule over the next several years, it was always phrased along the lines of: "if you are in the left lane and someone wants to pass you, you have to move to the right as a courtesy to other drivers."

Why is this a problem? Because without any prior knowledge of the rules of driving, a rational person will assume two things. First, they will assume that a speed limit of 60 miles per hour means 60 miles per hour. Second, they will assume that something which is phrased as a courtesy, does not apply if the other person is breaking the law. If someone else is approaching a door, it is a courtesy to hold the door open for them. But if someone has just robbed a bank and is running for the exit, the normal rules of courtesy do not apply and you are not expected to hold the door for them.

So, for several years, on freeways where the speed limit was 60 miles per hour, I would drive somewhere between 55 and 60 miles per hour, and - even worse - do it in the left lane. I assumed, as a rational person would, that the normal rule of "move to the left as a courtesy to the faster driver behind you" does not apply if the faster driver is attempting to break the law by doing about 70.

Now, put down your pitchforks, people, I said I don't do this anymore. But I think the reason this behavior enrages people so much is not just because the left-lane-drifter is slowing them down, although that's part of it. It's not just because they make people change lanes (thus incurring some small risk) to get around them, although that's part of it. It's because people think left-lane drifters imagine themselves as "vigilantes" who are slowing people down in order to enforce a speed limit that nobody, including the police, actually follows, and it's this kind of self-righteousness that infuriates everyone else. Myself, I never thought of myself as "enforcing" a law, I just figured I wasn't obligated to accommodate people who were breaking it. But apparently, that pisses people off enough.

So, I did this for years and years until I finally heard someone say: "the passing-lane law supersedes the speed limit law. In other words, if you're blocking the left lane, it's not a defense that you're going at the speed limit and therefore the only drivers you're blocking are the ones breaking the speed limit. You still have to move over anyway."

I said, "Oh, OK." And never did it again.

Like I said, a rational person will follow what they think the rules are and will assume that the rules supersede anything that is merely a "courtesy." If you want people to know that this is a law, then tell them it's a law, not that it's a courtesy.

If you tell people, "you should move to the right as a courtesy to other drivers," you are part of the problem.

If you tell people, "the law says you have to move to the right unless you're passing," you are less part of the problem, but not really actively part of the solution, because a rational person might still assume this doesn't apply if the people behind you are breaking the speed limit.

If you tell people, "the move-to-the-right law supersedes the speed limit law, so it's not a defense that the people behind you are driving too fast - you still have to move out of the way," then and only then are you part of the solution.

And yet, when Seattle's KING5 news station recently posted a story about left-lane drifters, a few people made comments saying, "I'm fine driving in the left lane because the people behind me are speeding anyway." Other people jumped in to correct them, as they should, however almost all of the comments were along the lines of: "you are a rude driver and you should move over as a courtesy to others." A few people mentioned that the law actually requires using the left lane only to pass. Not one reply actually spelled out the correct answer, which is that the passing-lane-law supersedes the speed limit law.

Why don't people try to educate left-lane-drifters in this way? My guess is that by phrasing it as a "courtesy", the lecturer gets to feel morally superior to the sinful left-lane-drifter, and by phrasing it as "simple" law - "The law says move to the right, dummy!" - the lecturer gets to feel intellectually superior to the ignorant left-lane drifter. The correct answer, which is that the law has some nuance to it - specifically, we have a speed limit law and a passing-lane law, but the speed limit law is superseded by the passing-lane law - doesn't allow the lecturer to feel either of these things.

So it's usually not given in these discussions, and another generation of under-informed drivers goes on doing 55 or 60 in the left lane, just like I used to do.