Is it ethical for me to take a shortcut that involves leaving an expressway a few miles before an overcrowded bridge and taking local roads only to re-enter the expressway just before the bridge. I have observed that much of the slowdown at this bridge is caused by merging traffic coming from this shortcut.

I'm not sure that ethics has much to do with it: whether to take theshortcut doesn't seem like a moral question. But your situation doeshave a paradoxical flavor: the very fact that you and others take theshortcut to avoid the slowdown at the bridge is what causes theslowdown at the bridge. If everyone could just agree not to take theshortcut, then there'd be no slowdown, and no need to take theshortcut. Of course, it's difficult to get everyone to cooperate. Andif somehow you could, it wouldn't last long: someone would realize thats/he could take advantage of that cooperation by taking the shortcutand notencountering any traffic at the bridge. And then another person wouldrealize that; and then another. Until enough people began taking theshortcut to cause a significant slowdown at the bridge. Philosophershave been very interested in such unstable attempts at cooperation whicheventually break down and leave all participants worse off than theymight otherwise be. (They've been baptized Prisoner's Dilemma situations.)What's of perennial fascination is that the breakdown is caused not byparticipants' failing to reason correctly about what would be in theirself-interest, but rather precisely by their correct reasoning about the situation. Reasoning well can leave one less well offthan one might otherwise have been. And such a situation attractsphilosophers like moths to a flame.

The expressions "Free Rider" and "Easy Rider" both fit nicely with this cute example. I'm not convinced (yet) that it is not a moral question. When I refrain from making that automotive move--or when I give in to temptation, and do it--I feel my moral sense at work. I'm a cheater, or I rose above the base human urge to cheat. I suspect that utilitarians, deontologists of various stripes, and virtue-ethicists all would have something to say, or pontificate, about it. Jan Narveson, by the way, would say (has said) that the fact that we have such crowded highways is a sign that our lives are getting better (and not, say, environmentally worse).

Update February 14, 2006: I took a passenger van from O'Hare airport in Chicago to a hotel in the Loop last Thursday. The cars on I-90 were crawling up each other's tailpipes. My driver scooted off the interstate at an obscure exit, zipped through the intersection (the light was green), and dove right back in on the other side. When I got out of the van at Club Quarters on W. Adams, I mentioned to him that I thought he didn't save any time by that maneuver. His reply: "Oh? I skipped past 100 cars." Not quite. There were 3 lanes of traffic. On my calculation, he skipped by 33.3333 cars. (Another update, 04/03/06: maybe he skipped by 300 cars!)

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