September 6, 2006

Boorish Benefit

I consider myself a courteous driver. I let people in, keep my composure in almost every situation, and try not to be an ass****.

Yet, like much of life, there are times when attempts at kindness have unintended consequences. I have long felt that one of these was "left lane closed in 2000 feet." The nice guy thing to do is to merge right, the ahem thing to do is to wait until the lane ends, then force yourself into the stream of good decent folk who merged early.

Attila at Pillage Idiot takes this on in Highway game theory.

My question is: Assume you have to comply with all traffic laws. You're on a highway with four lanes in each direction, and traffic is fairly heavy. You see a sign telling you that the two left lanes will be closed in 2000 feet. What's your best strategy to minimize the time you will be delayed? (Using the shoulder isn't a legal answer, because the traffic laws don't permit it.)

Let's call the four lanes 1, 2, 3, and 4, from left to right, where 1 and 2 are the left lanes that are going to be closed, and 3 and 4 are the two right lanes. Which lane or lanes do you drive in?

In spite of doing some time in Mathematics and the AI industry, my game theory is weak. My economics is slightly less weak.

The lane is a scarce resource, by merging early, you are increasing the scarcity -- why not use all 2000 feet? More significant still, all that early merging creates 2000 feet of stoppage. At the end of the lane, there is a natural merge point where everyone can choose the same spot.

Attila claims empirical evidence that it works best for the driver (he uses the nicer work jerk). I claim it's fairer and ultimately faster for everyone.


On the web Posted by John Kranz at September 6, 2006 12:51 PM

What I didn't mention is that efficiency is improved even more if, when you see that "lane closed" sign, you move into the lane that's going to be closed -- and use it until the last minute. I say "efficiency" because it seems more like jerk-itude. But I've tried it, and it works.

By the way, thanks for the economic analysis. Now I don't have to feel like such a jerk. I'm avoiding the use of scarce resources.

Posted by: Attila (Pillage Idiot) at September 6, 2006 3:30 PM

When you need a buzzword, man, I'm there.

You East Coast guys can move into the empty lane -- that will get you some severe disapprobation in a square state.

Posted by: jk at September 6, 2006 4:14 PM

Mathematics, artificial intelligence, economics... how about fluid dynamics?

I agree with Attila if the percentage of closed lanes is less than 50%, as in his example. If only 1 lane is closed on a 3 or 4 lane highway, however, the best place to be is... the lane furthest away. Once lane 1 ends, the traffic from lanes 1 and 2 is now squeezed into lane 2. Traffic will be least affected in lane 3 or, if it exists, lane 4 (since some of the traffic in 2 will move to 3 to escape the merging pressure.)

This analysis presumes that traffic is actually flowing at decent speeds. At very low speeds all the lanes move at about the same rate and Attila's solution works because you're passing parked cars (like his off-ramp example). In that case you are maximizing use of a scarce resource, it is true, but you're also increasing risk that you'll have to risk jerkitude when the scarce resource is exhausted.

Speaking of jerkitude, have you ever needed to merge from an on-ramp but another car was right next to you, blocking your merge? I give cars to the left the right-of-way so unless that traffic is clearly slow and I have a long ramp, I wait for them to pass before merging. Most drivers see this and speed up. Not the jerk I saw this morning. He had what I've dubbed "CCAAC" disease. "Cruise-control at any cost." You see these people in the left lane too, shadowing traffic for miles at a time as they barely, excruciatingly, overtake slower traffic. You know, the cruise control can be temporarily overridden by the accelerator for a reason you sanctimonious self-absorbed public nuisances!

Posted by: johngalt at September 7, 2006 3:30 PM | What do you think? [3]