Everyone knows that your gas mileage falls considerably once you reach high speeds, but how much? Bryan Caplan links to a number-crunching exercise by Jim Hamilton: the tax-free increase in incomes from slowing down to 65 instead of 75, under certain assumptions, could be about $20/hour, tax-free.

Caplan correctly points out that the stress of commuting is often what really matters, but I would guess that some of this would be alleviated if freeway leadfoots were to slow down. I find that the constant braking and accelerating that I have to do because of high variance in highway speeds is the most stressful part of driving--to say nothing of the traffic snarls that occur because of accidents. I took a forecasting class from Walter Enders during his first semester at Alabama; one of the things he said that has stuck with me is "speed doesn't kill. Variance kills." Thus, if the variance of highway speeds were to fall, we should also expect traffic accidents to fall.

I agree with Hamilton's claim that spreading the information about savings from slowing down is a public service (hence this post). Suppose there are two kinds of drivers, tortoises and hares. Tortoises are already slow drivers and have very little to gain from changing their highway speeds. Hares, who are sacrificing gas mileage for speed, have much more to gain from slowing down. Since hares should be more responsive to new information about savings from slowing down, we should expect to see lower variance in highway speeds and, therefore, less commuting stress and fewer accidents. If anyone has tested this (or plans to), please let me know. Mrs. Carden and I are driving from Great Barrington to Bryn Mawr, PA on Saturday (and then from there back to Memphis next weekend), and I know that this information is going to change our driving habits. The policy implication--again assuming that we can't end what Walter Block has called "road socialism"--is that perhaps we should re-evaluate the penalties for breaking speed limits. This, of course, then has direct bearing on our estimates of the correct Pigou tax.

UPDATE: A reader points out that the original title, "Increase Your Income by Slowing Down," isn't technically accurate.