Wednesday, July 05, 2006

How Cars Move — And Why they Don’t

Have you ever been stuck in traffic and wondered why nobody is moving? I’m not talking about heavy traffic where you crawl down the interstate at 20 miles an hour. I mean where as far as you can see nobody  is moving.

Barring some sort of obstruction in the road — like a major accident or a giant meteor — how can that be possible? If everybody is pointing the same direction on the same road and wanting to get to the same place, how can everybody be sitting still?

This was the question on millions of minds last fall as they attempted to “race” out of New Orleans while Hurricane Katrina was barreling down upon them. Highway officials had reversed the traffic flow on the interstates so extra lanes were available to leave town. Everybody had plenty of warning and they were all essentially going the same direction, i.e., away  from the city. So why did they spend so many hours just sitting on the highway?

The same thing happened a few weeks later as Hurricane Rita took aim on Houston. Tempers flared, cars overheated and ran out of gas, but for the most part people found themselves just sitting on the highway for hours at a time.

There’s a simple answer for this. Although cars are generally built to move very fast, they do not maneuver very quickly when they are in close proximity to each other. The closer together that cars are, the more awkward they are and the slower they are driven. It doesn’t matter that they are all going the same direction. It really doesn’t even matter if there are a lot of merging lanes. A congested highway is a slow one.

It’s easiest to understand this concept if we put it in human terms. Let’s say we’re at a major league football game in a packed stadium filled with 75,000 fans. In the middle of the game, an announcement is made that everybody must leave. But half the exits are blocked, so everybody needs to leave via the exits on only one end of the field.

Oh, and there are a few restrictions around leaving. The most important restriction is that nobody can touch anybody else. No touching. At all. Period. You can’t brush against each other, you can’t touch elbows, you can’t even place your hand on somebody’s shoulder.

To make sure nobody touches each other, you should keep a reasonable distance from each other — at least three to eight feet. No closer than that. And when the person next to you moves, you should wait two to five seconds before you begin to move.

That’s what it would be like if we applied the rules of the road on a human scale. Under normal circumstances, a large stadium could be evacuated in half an hour or so. My guess is that if we all had to act like cars, it would take all day to get everybody out of there. And there’d be a lot of people just standing around for a long time.

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