Friday, May 16, 2003

You're driving on a three-lane freeway (three lanes going in your direction, that is). Traffic is heavy and just on the verge of a slowdown. Then it happens: You see brake lights stretching ahead into the distance, and traffic comes to a stop. You wonder why. Perhaps some idiot got into a wreck.

Then you see it: A large orange sign reading, "Right Lane Closed, One Mile Ahead -- Construction Zone." And the response that other people have to this sign is to begin merging into the two left lanes. Thus, the traffic jam.

But here's the dilemma: As you pass the orange sign, you now see that virtually everyone ahead of you has already merged into the two left lanes, which are now at a complete standstill. Ahead of you stretches the right lane, almost completely free of traffic for the next mile.

Do you:

A) Merge into the two left lanes like everyone else, or
B) Drive at 60 down the right lane, and then merge at the last possible moment before the right lane is closed.

I say the answer should clearly be B. But I get the feeling, from having been in quite a few such situations, that most people don't agree with me, as evidenced by their behavior and by their refusal to let me merge at the beginning of the construction zone.

Here's why the answer should be B. The construction zone is a particular length -- say, two miles. For that distance, three lanes of traffic are going to have to be squeezed into two. And at some point prior to the construction zone, those three lanes of traffic are going to have to come to a standstill while people merge to the left. The point is, merging a mile ahead of the construction zone has the same effect as extending the construction zone. That is, if everyone is going to merge a mile ahead, leaving the right lane empty for that mile, you're in the same situation as if the construction zone were three miles long and everyone merged right at the construction zone.

In other words, it can't possibly be beneficial to merge ahead of time when traffic is heavy. All this accomplishes is to waste the right lane for the one mile approaching the construction zone, and effectively extend the distance for which all the traffic must squeeze into two lanes. It has to be a more efficient use of the road space to utilize the right lane to its full capacity for the entire distance, and then merge right at the construction zone.

Thing is, I'm not sure this principle applies when traffic is light. If there are few enough cars that you can easily merge ahead of time with everyone still maintaining their 70 mph speed, that might be preferable. This is because if you wait until the last second, you might have a hard time merging at 70, causing you to slam on your brakes, and thereby slow down traffic more than if you had gently merged ahead of time.


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