Links: Speeding up, slowing down, paying more and pedaling
Posted on May 8th, 2008 – 5:10 PMBy Roadguy
- Slower trucks: Schneider, the Wisconsin-based trucking firm, is lowering its company speed limit from 63 to 60 mph to save fuel costs; a story out of Milwaukee is here.
- Faster speed limits? This post says Utah drivers could be allowed to go as fast as 85 mph.
- Higher gas prices: Watching them climb is almost a daily ritual; a Strib story is here.
- Meet some local bicyclists: Click here for five vita.mn profiles.
- Free bikes for visiting Republicans: An AP story, via Minnesota Public Radio, is here.
- New driving rules? The Legislature is still working it out; one story is here.
16 Responses to "Links: Speeding up, slowing down, paying more and pedaling"
Behind Bars is my favorite bike shop in the whole world. I am excited to see it mentioned in the cycling article!
I feel guilty that I don’t cycle to work despite riding 25-40 miles per day for everything else. I was trying to figure out a way to bike to work, but then I realized I would have to get up at 4:00am to get to work on time by bike–my commute would be two hours one way by bicycle even with a rather high average speed–so that put an end to that idea.
Several co-workers brag about being able to bike to work at my place of employment; but they only live 2 or 3 miles away. Pfft.
WCCO had one of their “Good Question” segments on last week asking about speed limits. Basically, they’d go to people and say “speed limits help reduce gas consumption - is that a good idea?”
Well, sure, if you put it like that, who’s for more gas consumption. But, if you ask the question, as “would you increase your commute 10 minutes for a whole two quarters?” I’m sure you’d get very different responses.
…oh, and before people start debating times and money, relax. This wasn’t a scientific number, but simply pointing out that people already balance cost and time when they choose to speed - it’s just that time is winning.
Next Friday is Bike to Work day. Perfect chance to try it out!
…Except that most people have no idea how much gas they waste by going fast.
I’m not in favor of mandating freeway speed limits back to 55 mph, but people are making their decisions with less than perfect information.
I monitor my gas mileage, and in the past I have intended to slow down substantially and see what affect it had on my gas mileage. I tried it once and lasted . . . about 5 minutes. I couldn’t stand going so slow on the interstate while all the other cars whizzed past me. Some day I’ll try it again.
Perhaps gas is not yet expensive enough to incent people to slow down to save money. Personally, when booking airline travel, I am happy to pay more for less travel time. Usually that’s a factor of hours, but the principle is comparable. When I used to drive between the east coast & midwest, I figured if I could average 60, including stops, instead of 50, I’d save 4 hours. Cutting 4 hours off a 1200 mile road trip was worth the higher fuel costs.
I’ve recently read that both airlines and truckers are slowing down (albeit slighly) to economize on fuel consumption. Southwest Airlines reduced speeds on some routes, increasing flight times by 3-4 minutes. They estimate this will save them about $42 million per year.
This is definitely worth it. Whenever I fly Northwest (nee Delta) I expect to add 5 minutes before takeoff simply because they are unprepared or because there is a queue on the runway. If this type of adjustment can avert further fare hikes, I fully support it.
I wish my car had a MPG readout like some of those “fancy” cars, but being that it is a Ford Focus I am just happy when the key cylinder doesnt lock up. I’d like to see how MPG varies from say, 45 MPH on a straight suburban street (in 4th and in 5th gear) as well as on the freeways from 55mph up to 75 or so. Aero force (as I remember) is proportional to the cube of the velocity so I’d expect that MPG would drop substantially as speed increases.
There are aftermarket devices that can plug into the diagnostic port on your car (usually located under the dash or front seat) to give an mpg readout. I’ve got a ScanGauge, though I wish it would average out the last several seconds of data rather than just give an instantaneous estimate…
Unfortunately, what we see happen all too often is the decision making ability taken away from individuals through legislation. It should be left to an individual to weigh for him or herself time savings, cost issues, and any potential environmental impacts of burning more fuel in one’s own vehicle.
Alex, I agree. I say we start a promotion where we make sure everyone understands that the 55mph speed limit has nothing to do with safety and everything to do with gas mileage. Maybe people wouldn’t act like 55mph was the word of God.
bsimon: Perhaps gas is not yet expensive enough to incent people to slow down to save money. It’s not, and it’s not even close. People still drive when they could walk, refuse to carpool, refuse to use public transportation, etc.
And I hear it now, “But Prof. S., you are so anti those things on this blog.” Not true. I just am anti-forcing people to make those decisions or guilting them into irrational choices.
bsimon: Perhaps gas is not yet expensive enough to incent people to slow down to save money.
Should have said “perhaps gas is not yet expensive enough for people to stop driving like idiots”. I’m still amazed at how many people floor the gas pedal when there’s a red light a block away. I coast to the light and lose not a second more than the other guy.
Gas will never be too expensive to change, these roads are still congested…i was in virginia a couple weeks ago on a sunday and the road was packed with out of state licenses, these same people are the ones complaining about the fuel…No one wants to SACRIFICE a single thing… thats what it has come down to, americans have gotten way too spoiled, take everything for granted, think we shouldnt have to sacrifice a few minutes and PRIVACY to ride the bus or train, and think everything should be cheap or free…real life is starting to catch up huh.
I got 41 MPG in my ‘92 Saturn a couple summers ago, holding it right at 60 up to the north shore. However, people on I-35 obviously didn’t like my slower speed, so I exited at Sandstone and took MN-23 the rest of the way. I would have averaged 35 at 70 MPH. Unfortunately, said Saturn was stolen this week, so no more road trips for me (cue tiny violin.) Apparently thieves are into good gas mileage these days as well…
What is the predominant factor that determines mpg vs. mph? Is it the drag co-efficient of the vehicle, the vehicle’s weight vs. horsepower, or ? Obviously, a multiple of factors are involved, but when choosing a vehicle and they post the estimated mpg, what “city” and “hwy” speeds are they using in their estimates/calculations?
Pete:
The numbers on the window sticker aren’t meant so much to be warranties or guarantees, but more so as a comparison under similar conditions. The companies use estimates which takes an actual vehicle uses EPA mandated conditions, which “simulate” city and highway conditions.
Pre-2008 MY, those tests were based on an outdated methodology. For city calcuations, it assumed people drove in a limited band of speed somewhere around 30-40 mph, but never stopped. The highway numbers were based on speeds, I think of 48-55. That’s why your mileage varied so much. The new test is an improvement, though I don’t know the new methodology. I’m sure EPA has it posted somewhere on their site.
Mileage versus speed really does depend on a lot of things. I was an engineer in a former life, so I could get into really excruciating detail. I’ll try my best to keep it simple. At low speed, air resistance and friction are negligible. Therefore, while accelerating, your mileage mostly depends on how fast and how often you accelerate. The more you can slow down or speed up a bit (without breaking the law) to time the light, or the lineup at the stop sign, the better it is.
When accelerating, more horsepower means less mileage. Most engines and transmissions are designed to work most efficiently with engine speed around 1800-2800 rpm. As long as you can do it safely, that’s the most efficient range when accelerating. But clearly, if you have to accelerate more car, you need more horsepower (and more fuel) to do it, regardless of whether you do it with a bigger engine or a higher engine speed. The power/weight ratio mostly determines how quickly you will accelerate off the line assuming full throttle and full use of the horsepower.
Drag comes in at higher speeds, as does friction from tires, and other moving parts in the car. botski hit this point. At higher speeds, much more of the air flow around the car is turbulent, meaning that it is not flowing smoothly over the car. This effect increases exponentially with speed, as do many of the friction losses from tires and the engine.
To illustrate, here are some rough ballpark numbers, since so much depends on conditions. It may take 20 hp to maintain a speed of 50 mph, but it could take 40 hp at 70 mph and 70 hp at 90 mph. When turbulence is predominant, lower drag coefficients have less meaning. You may swim the 100 meter a bit faster in the pool with a spandex swimsuit, but in the ocean, the waves will slow you down far more than your swimsuit can speed you up.
