Saturday, July 12, 2008

Not That Thing Again!

The calls are picking up for reinstating a 55 mph speed limit to conserve gasoline. For those of us that did a good deal of long-distance driving during the Sad Seventies when this federally-ordered limit was in place, it made for great discomfort and irritation. A typical fuel efficiency curve shows a decline above about 60 mph, but other variables such as aerodynamics and weight are also important.

For Americans that drive as part of their employment - like truckers - this 55 mph limit is onerous. It means an additional 21% time on the road to deliver a given value of goods, and is physically gruelling for truckers. For a two-hour business trip (140 mi) in a vehicle that gets 30 mpg at 55 mph, the loss of fuel economy driving at 70 mph is 5 mpg, or less than a gallon of gas for the trip. The time lost at the slower speed is over a half and hour. If the employee-driver is making minimum wage, the savings in fuel costs for a 55 mph limit is lost in additional employee wages in the increased drive time, and a half-hour productivity improvment is lost (it takes more to execute a business transaction of a given value rather than using that time to execute additional business).

We believe that finding additonal sources of transportation fuels - oil, natural gas, electricity, bio-fuels - is a more important task than Share-the-Misery ideas like a lower speed limit.

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