Slow down, you move too fast

I know this will be a shock to everyone who drives in Houston, but so far the high price of gasoline does not appear to be having any effect on how fast people drive.

If drivers are slowing down to save money in response to soaring gasoline prices, the evidence was hard to find on the road last week in Houston.

Despite the fact that fuel efficiency for most automobiles drops sharply at speeds above 60 mph, a two-day visual survey showed sports cars, luxury cars, clunkers, motorcycles -- even a school bus -- motoring along at speeds that were neither economical nor environmentally friendly.

[...]

"You have to get where you're going," he said.

To check whether fuel costs had lightened motorists' feet as well as their wallets, a pair of Chronicle reporters and a photographer gassed up ($3.60 a gallon, regular) and hit the road Wednesday and Thursday afternoons with the cruise control set at 60 mph.

We covered all but two of the radial freeways, driving between downtown and Beltway 8, plus all of Loop 610, much of Texas 225 and half of the Sam Houston Tollway.

The tally: 1,021 vehicles passed us, and we passed 16, a ratio of about 64-to-1. On Thursday we were skunked 478-to-0.

We chose 60 mph because, according to the U.S. Department of Energy, most cars get their best mileage between 30 mph and 60 mph and because the legal speed limits on most of the area's freeways and tollway system are 60 mph and 65 mph.

[...]

About half the drivers seemed to be going only a little faster than we were, but the other half were really flying, so the average probably was around 70 mph.

Many of those in the biggest hurry drove some of the least thrifty vehicles, including pickups, SUVs and 18-wheelers.

Boy howdy is that even less of a shock. Knock me over with a feather, ya know?

Just a guess here, but I'd bet that a lot of people really haven't internalized the concept that increased speed means worse gas mileage. According to the government, which provides a handy if somewhat generic chart, "you can assume that each 5 mph you drive over 60 mph is like paying an additional $0.20 per gallon for gas". That's based on gas at $3.51 a gallon, so with prices already higher than that, you're sailing past $4 a gallon as well. I think people know at some level that faster driving means less fuel economy, but I doubt many of them have numbers in their head to make it tangible. You tell me - does putting it in these terms change your perception?

By the way, if anyone out there drives an RV, the effect is even more pronounced for those vehicles. You'll see your fuel economy cut in half as you go from 45 MPH to 70. Ouch.

Posted by Charles Kuffner on May 14, 2008 to Planes, Trains, and Automobiles