Slow Down and Save...Gasoline

Would Americans reduce highway speeds if they knew it could cut gas consumption by 8 percent?


When I was in high school during the Arab oil crisis of 1973, there was a lot of talk in our civics class about how driving slower was one way to use less gasoline. The next year, the Nixon administration put a national 55-mile-per-hour speed-limit policy in place, and it is credited in part for the decline in gasoline consumption that decade. However, years passed, oil prices fell, the speed limit policy was eased in the late 1980s, and any tie to federal highway funds was completely repealed as one of the first acts of Newt Gingrich's Republican Congress in 1995. Today, I doubt that many drivers think about the connection between speed and gas consumption.

So I was surprised to read in the Congressional Budget Office's recent study on the impact of high gasoline prices the conclusion that pain at the gas pump was causing many motorists to drive more slowly. The researchers looked at uncongested (weekend) freeways in California, where numerous automatic data collection devices have recorded large quantities of traffic data from many locations over long periods. After doing statistical tests to rule out whether the effects were due to seasonal or other factors, the researchers concluded that many drivers did seem to be easing off on the gas pedal. Perhaps a minority of drivers were having an impact, slowing the drivers around them—ever so slightly.

Essentially, the results translated to a 10 percent increase in the price of gasoline causing the median speed to decline by about 0.5 percent. (The slowdown was more pronounced for the slowest drivers on the road and nonexistent for the fastest drivers on the road.) That's saving a little gasoline—less than one-twentieth of a gallon per 100 miles or, as the CBO researchers put it, a teaspoon of gas every 2.6 miles.

But could we do better? The CBO researchers cite a study conducted by Oak Ridge National Laboratory showing that slowing from 70 mph to 65 mph—a 7.1 percent reduction—would cut a typical vehicle's fuel consumption by 8.2 percent. At $3 per gallon, the fuel savings would be worth 9 cents every 10 miles. Travel time would increase by about 4 seconds per mile.

I wonder if drivers think it would be worth it. From a policy standpoint, achieving an 8.2 percent reduction in highway gas consumption without doing a thing to improve cars seems pretty compelling. It's an idea on which politicians have been deafeningly silent. But maybe short of a mandate, there's a way of getting the word out that slowing down makes more sense now than ever. Bully pulpit, anyone?