What is Digg?449 Comments
- CSHYDRASHOK, on 05/22/2008, -23/+182***** That! thats way to slow
- lucidguru, on 05/22/2008, -10/+129As far as physics is concerned a relatively slower speed gets you more miles per gallon (MPG) than a faster speed because of drag. (Drag = 0.5 * airdensity * velocity^2 * carsurfacearea * dragcoefficient). This equation shows it is not a linear relationship: every time you double your speed the drag increases by 4 times. So the slower the relative speed, the less drag your car will experience. You also have to account for other factors such as the engine efficiency, the tires, the road surface, etc.
Slower speeds do not work though--> people just end up driving more ... Economics tells you that if you want people to drive less you've got to raise the price of gas.
Besides speed limits on the interstate hinder commerce and make communities less efficient... On most major highways the speed limit should be ABOLISHED. There have actually been a lot of studies on this subject and what has been shown is that people will naturally travel at the fastest speed that they feel safe. Speed limits are used to bring in revenue to small governments in the form of tickets and other fines. Ticketing the speeders does nothing to make the roads safer. To make the roads safer you've got to target the idiots on the cellphone, girl putting on makeup, and other people not paying attention. - HiCaP, on 05/22/2008, -3/+111I Can't Drive,,,, 55
- allaboutdatiki, on 05/22/2008, -5/+84A national 55 mile per hour speed limit would be a BIG FREAKING MISTAKE.
Helping people get the best gas mileage out of their vehicles, no matter the average speed, would be a much better idea. It's largely a case of education ... many, if not most, folks need to learn how to drive their cars for the best possible mileage ... whether that's at the posted legal limit or slightly above. - Iamonacomputer, on 05/22/2008, -3/+55What we really need is an alternative to gas or at least cheaper gas and not another law that wont really do anything but piss people off. The gas prices alone are incentive enough for me to drive 55 when ever i have the opportunity.
- QGYH2, on 05/22/2008, -11/+60***** it! We'll do it live !
- ejackso8, on 05/22/2008, -5/+42From a traffic engineering perspective this is a bad idea. Speed limits are mostly based off of the 85th percentile of what drivers are traveling at. By lowering the speed limit to below the 85th you institute a large speed differential between those driving normally and those obeying the posted limits, which leads to an greater amount of traffic accidents. In a perfect world this would work if everyone followed the posted speed limit, but that is not the case. Now this might help with the energy problems, but it would be at the cost of many more accidents.
- inactive, on 05/22/2008, -13/+45it's spelled "too"
- inactive, on 05/22/2008, -3/+35If we have to spell properly and drive 55, the terrorists have won!
- InfamousAtheist, on 05/22/2008, -6/+3755 MPH speed limit is a TERRIBLE idea. More speed differential, more time on the road, more angry drivers, more deaths, and bigger government to go with it. How does this help again? Oh, right, by supposedly reducing fuel consumption by 1%.
- dOOBiEx213, on 05/22/2008, -2/+26I hope these people aren't serious... 55 in a school zone...MAYBE.
- mcquitty, on 05/22/2008, -3/+25Why would we want the Federal Government to control that aspect of our lives again?
This is a state right, not a Federal law. Therefore, the only way the feds can enforce it is to force the states into accepting money with strings attached.
What's next? Mandatory exercise for the benefit of global warming? Carbon credits for breathing?
The Federal government should stick to what it is granted in the Constitution. - iceman0113, on 05/22/2008, -1/+23"I can't drive 70mph (the speed limit for the majority of my commute)" That's why we should abolish speed limits, because you feel safe at 70 so you can stay in the slow lanes while those that believe they feel safer at 70+ go stay in the faster lanes. Plus, every time someone gets pulled over, that's an automatic traffic jam.
- shank2001, on 05/22/2008, -2/+22If they REALLY want to save gas/lower pollution, FIX THE STOPLIGHTS! Here in Orange County CA the speed limits on the street are 50MPH in most places, but I have to speed up to 50, only to have to stop at the next light, and do the same EACH AND EVERY BLOCK! Getting rid of all the "stop and go" would save a LOT more fuel than lowering the highway speed limits! Acceleration is where the fuel is really used the most. There are places in the country that have timed their streetlights so that if you go the speed limit (or a bit over) you hit greens pretty consistently. Also, study after study has shown that 55mph on the highway causes more deaths overall, due to the people who speed are still going to speed anyway, and the difference in velocity is greater between someone going 80 vs 55 rather than 80 vs 65-70.
I don't know why environmentalists always choose the stupid fights to fight. I am all for conservation/environment, but lets go after the most effective things, and do things smart! For example, ban.... or put stronger regulations on gas powered leaf blowers. Have regulations on all of those kinds of things, actually, eg. gas weed trimmers, lawn mowers, ATVs Motorcycles, etc. etc. Running a lawnmower for 1 hour is the equivalent to driving a car for 10 hours in terms of pollution etc.
But last on the list should be lowering the speed limit to 55!!!! - dusanmal, on 05/22/2008, -2/+21Physics you describe is idealized. One must take in account efficiency of the engine both vs. load and vs. speed/rpm. In 1970's 55 mph was correct number, due to the junk engines and insane non-aerodynamic cars.
As counterexample: it is more fuel efficient for most modern cars to coast in gear than in neutral. Because idling engine without any load wastes a lot of fuel (poor efficiency).
Hence, as long as the driver drives at the quite steady speed some increased air friction and drag actually helps the engine work more efficiently and use less gas for more work... Combined with modern engine design that typically places optimum efficiency at higher speeds (depending on the car) you could get better fuel efficiency at 70 mph vs. 55 mph in many cars. 55 mph likely still works well for SUV's and such. Too bad cars are not regularly tested for this. - umbriago, on 05/22/2008, -7/+25Teach people to drive properly - not race up to red lights (which I see ALL the time), that sort of thing - is better than mandating 55. People won't obey it anyway. I commute at 50 mph and pull 37 mpg now; you think I'm in a big hurry to get to work anymore? Nope.
- xBreakdownx, on 05/22/2008, -7/+25***** THING SUCKS
- antonio97b, on 05/22/2008, -0/+17Notice how you didn't say slightly under.
- flip360, on 05/22/2008, -0/+16And here's a nice graph showing 95 as optimum:
http://i25.tinypic.com/azj48k.jpg
Both hold the same (read:NO) weight without references or research. - dubbleenerd, on 05/22/2008, -1/+17the spending on just educating people on how/why to switch to digital broadcast television has run up a tab of $1.5 billion. How much do you think it would cost to "educate" people on driving correctly?
- BlackJackJester, on 05/22/2008, -2/+16The best idea I've ever heard is to mandate MPG meters in all cars. When people are actively shown their mileage, many become very conscious about it. Its also been shown that higher speeds don't lead to more accidents, and people don't even drive 65 now. most go 75-80.
- catalysis, on 05/22/2008, -9/+22Screw it, we just need gas to go up to like $15/gallon. It's like peeling off a bandaid, you just have to get it over with.
- URnotheonly1, on 05/22/2008, -1/+14HOWS THAT FREAKING OWL DOING?
THANK YOU BABY BOOMERS! Could be 30 years into domestic production, could be 30 years into nuclear energy, we could of had all of this, but you said NO. You said you were not going to leave an infrastructure for later generations, BECAUSE YOU KNOW BEST.
You failed your country, your children and their children. - WiseWeasel, on 05/22/2008, -3/+15First of all, who drives the speed limit? Everyone knows you're supposed to drive 5-10MPH above it at all times. Second, if you ARE going to be driving at the speed limit, then you can't be complaining when people are passing you. Just do your thing, drive safely, and look behind you before changing lanes, and it shouldn't be a problem that the car passing you is going 15MPH faster than you.
- bradleyland, on 05/22/2008, -0/+11It wouldn't hurt if municipalities worked to _increase_ traffic flow efficiency, rather than degrade it. A common tactic in urban settings is to intentionally time signal lights so that you have to stop at every (or every other) one. This is done in the interest of decreasing speeds on surface streets, but it is hell on your gas mileage.
- inactive, on 05/22/2008, -2/+13driving slower over the same distance uses less gas than driving faster, yes
that's why some airlines are even lowering their engine speed during flights to save money
it's physics - inactive, on 05/22/2008, -0/+11I - can't -drive - fifty - fiiiiive!
- sullyz0r, on 05/22/2008, -4/+15Drag is far from the most important factor, the one you need to consider most is engine efficiency.
Here's a nice graph showing 55 mph as optimum.
http://www.grinzo.com/energy_old/graphics_misc/mpg ... - masterc, on 05/22/2008, -2/+13Like I'm going to trust some graph made in MS Paint...
- fr0stb1t3, on 05/22/2008, -4/+15While all that is true, you forget to take into account different motors are most efficient at different RPM ranges, so it depends on how the car is geared. I get better gas mileage at 78 than I do 55.
At 78mph, I get nearly 32mpg. At 55 I get around 26. - beersnob, on 05/22/2008, -1/+12Speed limit legislation will not slow people down. Lower it to 55 and in Texas, I can guarantee you people will still drive 70+. Speed limit enforcement on the open highway in Texas is nonexistent anyway. Lowering the speed limit to 55 again would be a joke. People will by god slow down, however, when they have to stop every 200 miles to put $100 worth of fuel in their Suburbans and Excursions! Let the speed limit be dictated by economics. I already see people slowing down--even in the wide-ass-open Lone Star State.
- zSlider, on 05/22/2008, -6/+16If you want to protect the drivers, avoid accidents, and decrease commute times, decreasing speed limits is not the way to go. Heck, the speed limit in the first place may be the cause of those negative things. A safer, quicker, (and possibly even cleaner) approach would be to do away with the limits completely. It is the variation of the car speeds that causes most accidents, and traffic backups. The real goal should be to minimize the standard devision of vehicle speed but, in order to accomplish that successfully I believe we would need to give up some of the control we have over our cars (as seen in "I, Robot").
- nizzy1115, on 05/22/2008, -0/+9The speed limit in Illinois is 55 on the highways already. However, everyone travels 75ish on average and many drive more than that. Heck i cruise behind state troupers doing 75.
- FeartheKnighted, on 05/22/2008, -2/+11Drag doesn't become a factor of velocity squared until a Reynolds number of about 1000 (which is approximately 70-80 mph for a sedan). Below that it is a linear relationship.
- bradleyland, on 05/22/2008, -0/+9Really? I drive a VW GTI, which is a compact, four-cylinder car. My indicated fuel efficiency at 75 MPH is around 24 MPG. At 55, it is around 32 MPG. That's a significant difference.
Still, I believe it should be my choice to take advantage of that efficiency, not mandated. - Fizzle, on 05/22/2008, -1/+10Blame your taxes. If you take away all taxes, you actually pay LESS per gallon/litre than we do.
- MovieQuest, on 05/22/2008, -0/+8Hagar's NOT gonna be happy.
- Nesh, on 05/22/2008, -3/+11Is that a gas guzzling airliner on your icon?
- DevilInPgh, on 05/22/2008, -0/+8Sammy Hagar FTW!!!!
- Gndoab, on 05/22/2008, -2/+10whatever country you are from uses oil as well.
- wynja, on 05/22/2008, -14/+22With increases in the technology of aerodynamics applied to cars. The difference in fuel efficiency between 75MPH and 55MPH in modern cars is negligible.
- superkendall, on 05/22/2008, -0/+8I was going to post the same thing, it will help a lot more where it matters like accelerating too fast or driving wastefully in hills.
- SirvonRohr, on 05/22/2008, -2/+10I commute 42 miles each way to work and now drive the speed limit. I get 3mpg better and it only costs me about 4 minutes.
- inactive, on 05/22/2008, -0/+8That's very true.
My girlfriend can drive 50 miles and use twice as much gas I would use in the same 50 miles using the same car. She has no idea about coasting or using the correct gear. - crash331, on 05/22/2008, -0/+8There are many facotrs involved (engine, transmission, etc.) but the #1 reason driving slower gets you better mileage is because of drag.
My car has a gas mileage computer and at 55mph I can get about 35-37mpg. At 85, I get about 23-27mpg. - geometry, on 05/22/2008, -0/+7I agree with a lot of what you said. Cops should go after the slow people in the fast lanes, they're the real danger.
- proliance, on 05/22/2008, -1/+8Don't worry, the Feds were sued and lost the right to set the speed limits on Interstates. Since they don't enforce the speed limits and don't provide the states any money to enforce the speed limits they have very little say in the matter.
The author of the article hints that he knows this, so buried as lame. - strangewill, on 05/22/2008, -2/+9For some reason people who drive trucks typically think faster == more efficient, as if physics need not apply.
- chrisaug18, on 05/22/2008, -0/+7Oooh so is this is what the song was talking about...learn something new everyday. Oh, and good song.
- MikeSD34, on 05/22/2008, -1/+8Gas isn't the only thing that's affected by the rising cost of oil, food, plastics, electronics, EVERYTHING is affected. It's a problem for the whole world in every sector, not just America.
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