Friday, July 11, 2008

55 MPH

I've been advocating (in my desultory way, here, here and here) that people drive 55 miles per hour (or as close to that as possible) as a way to cut down on greenhouse gas emissions. Here's a guy I disagree with on the issue (from the New Haven Register):

Greg Amy of Middletown, a member of the National Motorists Association, can't imagine Connecticut drivers ambling along at 55 on a clear stretch of highway.

"People don't obey these artificial speed limits. ... All it's going to do is make criminals out of people driving safely to where they're going," he said.

While Amy said "nobody will dispute with you reasonably" that slower speeds save fuel, "people are not going to drive (55 mph) so ergo it doesn't work."

I love his reasoning: People won't drive 55 miles per hour because people won't drive 55 miles per hour.

Of course just because I think it's something we can achieve doesn't mean I think it's something that will be easy to achieve. But people have come close to giving up cigarettes because as a society we've been convinced that it's bad. We can do the same when it comes to driving slower as a way to cut greenhouse gasses.

By the way, don't forget to sign up for Chris Zurcher's Connecticut Environmental Headlines (which is where I found the Register story; Chris has been taking some days off lately, which makes it harder for me to blog, so if you sign up it will encourage him to keep going)>

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Blogger Bloggo said...

I drove to my folks last weekend (over 200 miles round trip) and kept it 55 all the way. The gas tank needle definitely moved less and it's easier to react to the crazy drivers at 55 than it is at 70. Everyone should try it.

11:30 AM  
Blogger Dave said...

The added labor costs to business paying for employees being on the road 28% longer is far above the savings in gas. That added expense will ultimately result in increased prices of all goods and services.
55MPH will be very detrimental to the economy. Yes, many vehicles do get up to 27% better gas mileage at 55 MPH as compared to 75 MPH. However you are also driving 28% slower at 55 MPH. A 100 mile trip takes all most 30 minutes longer at 55MPH as compared to 75MPH.
For the sake of discussion, let's use the your math for the 100 mile trip: A car that gets 25 MPG would get 31.75 MPG at 55 MPH (27%) - Gas at $4.00 per gallon - Employee labor cost of $15 per hour.
Driving at 75MPH will take 80 minutes and cost a total of $36.00 in gas and labor costs
( use 4 gallons of gas at a cost of $16.00 and the labor cost would be $20 (1.3 hours x $15/hour))
Driving at 55MPH will take over 109 minutes and cost a total of $39.87 in gas and labor costs
( use 3.15 gallons of gas at a cost of $12.60 and the labor cost would be $27.27 (1.8 hours x $15/hour))
THAT’S AN 11% INCREASE IN COSTS BY SLOWING DOWN TO 55MPH. The burden labor rate for many service industries is actually $25 to $ 35 and more and therefore the problem is even worse.
The saving lives argument has also be very exaggerated. The chances of being involved in an accident on the highway increase the longer you are actually exposed to the risk. In other words, if you are on the highway an additional 30 minutes per day, your exposure to potential risk has been increase 30 more minutes. Being on the road longer also greatly increases driver fatigue. Driving while sleepy is as dangerous as driving drunk.
The claims that the National Highway death toll went down around 1974 due to the 55 MPH limit imposed after the 1973 Oil crisis has often been disputed. It has been suggested that this drop was actually due to new enforcement of seat belt laws and people driving less because of high gas prices.
As a business owner of a service industry, the interference by the Federal Government to make me inefficient will cost me thousands of dollars. Those who want to drive at 55 are more than welcome to drive 55. Just don't make everyone else along with the economy slow down with you!

6:43 PM  
Anonymous Bryan said...

I drive 55 but push it up to 60 when the speed limit is 70, to keep from getting killed. I may actually break the law and exceed a 40-mph speed limit by a few mph to keep my auto transmission in higher gear and the engine at lower rpm.

As for the National Motorists Association, I looked at the web site and was reminded of the NRA. The NMA's suggestion for improving gas mileage? Get rid of airbags and other safety features. Nice.

6:50 PM  
Anonymous Bryan said...

Then why are other service business purposely slowing down their trucks to save fuel? And why do you ignore the impact of fuel savings on our economy by reducing oil imports and improving our balance of trade. You don't think those will benefit our economy?

Hey, let's do whatever doesn't hurt Dave's wallet.

7:37 PM  
Anonymous Rick said...

Another problem with Dave's calculations is that he's using numbers obtained from a stationary vehicle on a testing device. Air resistance becomes a much bigger factor as a vehicle's velocity increases, and his figures don't take that into account.

8:27 AM  
Blogger Sam said...

Dave might have been referring to the amount of time spent in traffic congestion in urban cities, which is truly a staggering amount of money in the hundreds of millions. Every year Texas Transportation Institute does a study about how much time, gas, and money is wasted on congested travel, which is statistically derived as being Level of Service below C. For example, you'd be going less than 30 MPH in a 60 MPH highway zone; LOS D and E are bad "bumper to bumper" traffic, and there is a special LOS "G" for the Los Angeles Freeway.

As noted, many trucking companies have restricted their trip computers to speeds such as 54 to 59 MPH because wind resistance and tire friction losses operate at the power of two (x-squared) when over those speeds. Commuter cars are not as sensitive to such parasitic losses but do "waste" fuel when operating faster than 54 to 59 MPH (the most economical in the laboratory tests are 47.5 MPH, although that's not "real world").

There is evidence that slowing traffic and having everyone go the same speed can actually lower gasoline use, time traveled, and accidents. The Japanese are leaders in this kind of study, and have looked into putting sensors on vehicles to maintain a certain distance from the vehicle in front of it, and to smooth the throttle performance. This intuitively makes some sense because "jackrabbit" driving with heavy braking and throttle application wastes vast amount of energy, in addition to creating opportunity for lane conflicts that can result in accidents. -sam

12:29 PM  
Anonymous Bryan said...

Yes, I question Dave's calculations, too. A car that gets 32mpg at 55mph is more likely to get 20mpg at 75, given that the power required varies with the cube of the speed (i.e., going twice as fast requires eight times the power due to wind resistance and drag). His fuel savings would be closer to 2gal (and not less than 1gal as he calculated).

Dave's model is based on driving a car that gets 32mpg, which is pretty good these days. More likely, the car gets 25mpg at 55, so his fuel consumption drops well below 20mpg when he races up to 75mph. So the fuel savings is even greater (over 2gal for a 100-mile trip).

But in Dave's world, saving 2gal of gas a day and improving our balance of trade to support the dollar doesn't matter. "Dave's World" must be a nice place to live. If you're Dave.

1:34 PM  
Blogger Dave said...

Byran, Rick and Sam,
There are a lot more effective
things that can be done (and must be done) to improve driver safety, help the environment, and reduce oil consumption. The 55MPH speed limit is not it! I own a business and all of the service vehicles that we use get in excess of 30MPG. We recycle. Our dispatchers carefully route out service calls in the most effect route possible. I believe in safety. I make sure our vehicles have airbags, DSC and antilock brakes. However, the evidence that a mandatory 55MPH limit will save lives is just not there.
You do the math or if you would like help, I'll do it for you. What percentage of increased fuel efficiency do you really think the average car gains going 55MPH from 75? What MPG would you like to use?
I respect your motives but I personally feel that your passion may not be allowing you to look at the figures objectively.

11:15 PM  
Anonymous grot said...

Thank you very much. This was a great help.

7:55 AM  
Anonymous Anonymous said...

In regards to why the trucking industry would want to limit their speeds to 55MPH is simple economics. Freight is charged by the mile. Truckers are paid by the mile and not by the hour. There are no labor cost to be saved for that industry.

7:23 PM  
Anonymous Bryan said...

I'm not addressing the "saves lives" issue, so I won't argue it.

As for looking at the figures objectively, the figures I'm looking at address our national economy and the balance of trade, which is out of whack due in part to our need to import oil for transportation. You are focusing on your P&L, which is what a business owner should do.

I'm puzzled by one thing. You write as if 75mph is the norm and 55mph is the goal. I've only encountered 75mph on certain roads in certain states. Are you pushing to increase the speed limit to 75mph or some safety-based limit from the current 55?

Finally, yes, help me out. How do your 30-mpg vehicles do at 55 and 75? Thanks.

11:51 PM  
Anonymous Bryan said...


This is a bit OT (and has nothing to do with Dave) but did you read the Newsday piece by the Hofstra ethics professor who tried to fight his speeding ticket for doing 75 on the LIE? His arguments were ignorance of the speed limit and "everybody does it".

If I hadn't lived on LI before, I'd be asking what is in the drinking water that has slanted ethics to the extreme? I realize it's a sweeping generalization, but if an ethics professor doesn't get it, can we blame the double-dipping school board lawyer, the corrupt town planning commissioner and building inspector or the school superintendent for their ethical lapses? [A rhetorical question, of course]

10:32 AM  
Anonymous Tom Andersen said...

I'd like to see somebody do the math too although this website ( says it pretty clearly:

"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 $4.08 per gallon.

Bryan, I missed that Newsday story. There's obviously no shortage or hypocritical acts, or rationalizations.

By the way, to show that I'm a true American, I put 500 miles on my Honda on Sunday and Monday, much (but not all) of it on Interstates, and I can attest once again that if you drive 60, you're the tortoise, not the hare (with the important difference being that you don't win the race).

4:55 PM  
Anonymous Leigh Smith said...

Before you all rush off to the polling booth to create laws that are easily enacted and last 30 years after you forgot what it was that you voted for, lets take a deep breath and take a look at what your doing.

Firstly this is not the 60's and the vehicles we drive today are not your gas guzzling V8 muscle cars we all remember.

There is no gas shortage. You can drive anywhere in the USA and you won't find a gas line anywhere. What you will find is higher prices and plenty of people that will grumble a lot and shell out the money to fill their tank. They will head off down the highway and some will drive economically and others will drive the speed they need to drive to get where they have to go in the time available to them.

If you need to save a buck and drive 55 then more power to you. What do you care if the guy at the next pump is going to get less mileage than you do? Are you paying for his gas? Do you think that if we all drive 55 that gas prices will go down? Your dreaming! Gas prices have to rise to make it viably economical to drill for oil in our own back yard. What your seeing at the pump is a primer to get the american people used to paying higher prices for oil that needs to be drilled here at home where it costs more to drill and recover than it does in the gulf.

Perhaps your in no hurry to get where you have to go and you can quiet comfortably drive along at 55 and be relativly happy but I don't think thats your real motive to enact laws. The fact is your driving 55 because thats what fits your budget and it seriously ticks you off that others don't need to save a dollar and continue past you at 70 which makes you want to create a law that will make you comfortable and smug in knowing that you voted to police everyone else into doing what you wanted.

So drive 55 if you want or need to but just remember the price of gas is not ever going down and your sacrifice will do nothing to ease an oil shortage that doesn't exist. What it will do if you enact laws is to put more money into states pockets in the way of fines for motorists and raise premiums of insurance rates for motorists that get ticketed for "speeding". Perhaps that will also make you feel better as you amble off to grandma's house on sunday afternoon at rediculously low speeds that do nothing more than create traffic jams and frustration for your fellow citizens.

10:45 AM  
Anonymous Tom Andersen said...


I haven't been advocating that the speed limit be changed to 55. Instead, I think the states should start a public education and persuasion program designed to get people to slow down by telling them they'll save gas and money, and reduce their carbon footprint, just like they persuaded people to stop smoking cigarettes by telling them it probably would kill them.

Also I couldn't care less what other people can afford to pay. My main reason for advocating this is that it would seem to be a quick, easy and relatively painless way to reduce greenhouse gases in the short term while we're trying to figure out how to really reduce them for the long term.

2:01 PM  
Anonymous Leigh Smith said...


It's all smoke and mirrors. They didn't persuade people to stop smoking .. they shamed and priced them into quiting. The world will do just fine on its own and will be here long after all of us are gone. Maybe we should import oxen and bicycles from china. I hear they don't need them anymore since they are all driving automobiles.

10:51 PM  

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