Thursday, July 17, 2008

Drive 55

Peter Aplebome, the terrific Our Towns columnist for the Times, is on the look-how-much-energy-we-waste beat. A few weeks ago he wrote about the appalling practice of some shops in Manhattan of keeping their doors open and air conditioning on during hot days (which seems to me to be akin to an appalling practice of supermarkets, namely keeping large refrigerator cases doorless and open).

Today, Appelbome writes about driving 55 miles per hour.

The experts say that fuel efficiency deteriorates radically at speeds above 60 miles per hour. Every 5 miles over that threshold is estimated to cost drivers, Mr. Warner said in his letter, “essentially an additional 30 cents per gallon in fuel costs.”

Yesterday I added a comment to a thread of comments on this post, in which I referred to this website, which says:

Aggressive driving (speeding, rapid acceleration and braking) wastes gas. It can lower your gas mileage by 33 percent at highway speeds and by 5 percent around town.

... While each vehicle reaches its optimal fuel economy at a different speed (or range of speeds), gas mileage usually decreases rapidly at speeds above 60 mph.

You can assume that each 5 mph you drive over 60 mph is like paying an additional $0.30 per gallon for gas....

That's based on gas costing $4.08 per gallon, by the way.

Appelbome goes on to quote a handful of people saying, essentially, that to get them to drive 55, you'd have to pry the steering wheel from their cold, dead fingers:

“It’s unrealistic,” said Darren Jacobs, an engineer from Grantham, N.H., who was driving home from Macungie, Pa. That is a trip of 412 miles, or 6 hours and 47 minutes, according to MapQuest. So assuming 25 miles per gallon, driving at 55 would likely cost 40 minutes and save at least $7. He figured he’d spend the money.

“It’s too slow,” Mr. Jacobs said. “It’s not the way we live. Everything is fast. We eat fast food. We have high-speed Internet. If you’re going from Point A to Point B you want to get there as soon as you can. I don’t think the solution is making us go slower. It’s getting tough on the greedy people who are profiting from this.”

Pete Boucheron, a retiree from Schenectady, N.Y., said, yeah, there’s some logic to 55, but it might have more appeal if prices got really high, say $6 or $7 a gallon. Gustavo Cardenas said he was for it — but then, he’s from Montreal.

Of course this is both baloney and true -- baloney in that all they have to do to change, is change; true in that as long as everyone else is driving 70, they will too.

I think a 55 mile an hour law probably would be a good thing (and of course the speed limit on a lot of roads still is 55 miles per hour).I also continue to believe that a pervasive and clever public service campaign that emphasizes both the amount of money you can save and the amount of greenhouse gases you can avoid emitting would be effective. It's worth a try.

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Blogger Sam said...

True, for interstate highways, the FHWA usually sets rural speeds at 70 and urban speeds at 55 to 60 MPH. State highways follow a similar scheme as well. Cities can petition these authorities to reduce (or I guess increase) those speeds based on safety issues.

Here's an interesting concept - people usually drive "4 over" meaning when the sign says 55 they'll drive 59 on average, especially when the road isn't congested. There's some math behind this. The FHWA conducts speed surveys and uses the 90th percentile. So you shoot 100 vehicles with a radar gun, write down the numbers in an Excel spreadsheet, sort the numbers from high to low, and pick the 10th row from the top. Now you know that the cops actually expect to be able to write 10 percent of the cars a ticket! It's all about the money.

When it comes to excessive speeds over 60 MPH, that was always some kind of "freedom" issue. If everyone is going 70 and it works and accidents do not increase (they do on rural arterial roads but less so on urban interstates), why shouldn't I be free to drive 70?

This puts politicians in a very tricky spot, as they want to appear to have some enviro cred but also like to champion redneck "freedoms." In many cases this ends up as being an ineffectual, voluntary measure.

From a public policy perspective, speaking of energy and traffic safety, it is more than clear that 55 MPH would save tons of money. Perhaps such rational discussions can be had after the November Elections. -sam

12:40 PM  
Anonymous Bryan said...

So, according to your fuel economy site, going from 60mph to 75mph costs an extra $1.50 @ 30 cents/gal. That's an increase of almost 37%, so a car that gets 32mpg at 60mph will only get 23mpg at 75mph. Those figures are consistent with what I figured based on the increase in power required due to wind resistance. I hope Dave from your earlier post is still following this.

The folks quoted in Aplebombe's article are all addressing the money issue, which misses a big point. That extra $7 they're spending by driving 75mph is leaving the country and killing our balance of trade and the value of the dollar. Drive slower and spend that $7 you save on something that will help your local economy. Use that extra 40 minutes to listen to another chapter or two of a book on CD. I'm not arguing that 55 will lower fuel prices (I think they need to stay high) but it will help our economy.

As far as being the tortoise traveling at 60, I hear you. When I'm moving at the speed limit and I'm being passed left and left (not left and right because I stay in the right lane), I say to my kids, with tongue mostly planted in cheek, that those drivers passing us "hate America and support the terrorists". I know it's harsh, but don't these people know we're at war and our economy is going to hell because of our addiction to oil?

Sam makes a good point about the freedom aspect, but people seem to have tunnel vision. Many of my fellow citizens have no problem giving up the right of habeas because we're at war, but take away their "right" to drive 75 and they freak.

2:10 PM  
Anonymous Anonymous said...

i'm not sure where you are getting the 32mpg all the way down to 23mpg figures, but that must be the most aerodynamically inefficient car ever made. i get 39 miles per gallon at 60mph. i get 35 miles per gallon at 75mph. so on a 400 mile trip (which i do regularly for business), i'll spend about 5 dollars extra, but i'll get there 1 hour and 20 minutes sooner. time is money. the 5 dollars extra in gas is inconsequential.

2:05 AM  
Anonymous Bryan said...


Sounds impressive; only an 11% increase in fuel consumption. It seems to defy most everything I've read, but I'll give you the benefit of the doubt.

So, what car (a) gets 39mpg at 60mpg and (b) only suffers an 11% loss in fuel efficiency at 75mpg. I'm dying to know.

12:25 AM  

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