How do truckers feel about drafting?

Discussion in 'Gen 2 Prius Fuel Economy' started by Kinare, Apr 24, 2008.

  1. Huntceet

    Huntceet Junior Member

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    My comment on drafting comes from my cycling. When someone comments they can't catch a draft off me because of the kind of bike I ride my answer is "Real men push their own air."

    Hunt

    "Work like you don't need the money, love like you never had your belongings set on fire and dance like you're not wearing any pants."
     
  2. N3FOL

    N3FOL Member

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    Re: Safe Drafting Distance?

    I love the idea of drafting and the improvement in mpg, but I don't think that I can take all that paint chip on my front bumper and hood. I am staying much farther away from those big trucks. Not safe at all.
     
  3. a priori

    a priori Canonus Curiosus

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    To All: Great post with truly valuable information.

    The temptation to draft is so great when you are penny-pinching. I did this going cross-country in my VW (college days), and I truly felt like I could have turned the engine off on some days. Of course, the truckers often times could not possibly have known I was there, because I travelled so close -- so ridiculously close to those big rigs.

    I appreciate the emphasis on safety expressed in this post.

    I am (almost) always thinking about mileage, but it comes in third place in my driving priorities behind Safety and Courtesy.

    I think it is pretty clear where drafting 18-wheelers fits in the scheme of things.
     
  4. Boo

    Boo Boola Boola Member

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    a priori,

    Lol, that's what I did my cross country trip in too, a VW. Ours was a Squareback and we were transporting it to Washington. But when we drafted behind tractor trailers, we were usually around 100 feet back.
     
  5. a priori

    a priori Canonus Curiosus

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    At this point I wish I could find the records I kept on that car. I always maintained a full log of everything I did on and to my cars, including a mileage chart. I know I had incredible mileage on that thing when I did those cross-country tours (yes, I did this more than once!) between MN or IL and CA.

    How crazy! I am pretty certain my memory is reliable on this one: I do believe I was able to place the car in neutral on many flat stretches. I couldn't do it on downgrades -- I needed the engine resistance to keep me back!
     
  6. Evilshin

    Evilshin Member

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    The prius is too aero dynamic to make a huge difference drafting in normal winds. However when there is a strong head wind, yes it makes a difference.

    This is because wind resistance in terms of energy use is perportionally cubed with respect to speed. During strong head winds (40 km/h+) you will experience a bigger difference in air speed farther back from a semi too... So it makes sense then...

    But in still air and tail winds... forget about it... the only fuel savings you will get is due to the fact that the semi's don't speed much (in ontario...).

    Always keep 2 seconds behind the vehicle ahead of you...
     
  7. darelldd

    darelldd Prius is our Gas Guzzler

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    A wee bit of the subject here, but this is right up my alley. Do people really think that the quality of your draft is determined by the BIKE? Hello? The RIDER is what you're drafting behind, the aero of the bike is all but insignificant compared to the barn door that's riding it! I'd rather have a bikeless human in front of me going 25mph than a riderless bike doing the same!
     
  8. coot

    coot New Member

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    As a truck driver for 38 years as someone put it earlier I too think you are an idiot. the highways and surface streets are not Nascar tracks with a bunch of professional drivers. Remember if you are so close you can't see the trucks mirrors, he can't see you. More than once I have seen a piece of a truck tire recap or other garbage laying in the road and due to the ground clearance of my truck I was able to straddle it, but you being in a car with a lot less ground clearance, besides a much reduced reaction time due to following so close to draft to try and save a couple more mpg's risk serious damage to your car or serious injury or death to yourself or others in your vehicle. Next time you're out on the highway check out all the junk on the road. If a tire on a big truck comes apart and they do, it could come off in small pieces or a piece a couple of feet long and weigh quite a bit. It will do a lot of damage to your car. If you happen to be that close to a truck when it happens the piece could come through your windshield and take you're head off. I know of that happening to a family of four, they where all decapitated. It does not even have to come off the vehicle you are drafting, it could be kicked up windshield high just by bring run over. Put a little thought into what might happen doing something stupid like drafting. All it takes is a split second of taking you're eyes off of the vehicle you are following to look at the radio or some other distraction and the driver in front of you reacting to an emergency and wham, you're lodged under the rear of a big truck and he may not even be aware of what has happened because you were so close to him he couldn't see you. I was first on the seen of an accident where a Cadillac at night with no lights on hit the rear of a tanker and was dragged for miles down the road. The only reason he stopped was the shower of sparks coming from the rear of the tanker which was loaded with a flammable liquid. He said it felt like he had hit a bump in the road. It totaled the car and put both drunks in the hospital. But don't think that you getting killed doing something foolish affects the driver, I will never forget what a body burned beyond recognition smells like or his screams while burning to death when I could not get him out. Or how much a severed at the shoulder arm weighs that I had to pick up. But what bothers me most is the lifeless body of a mangled child that did not have to die. I don't draft in my big truck, car or motorcycle, it's just not worth the risk.
    If at all possible STAY AWAY From BIG TRUCKS. you don't stand a chance against a loaded 80,000 lb truck, even an empty tractor trailer can weigh over 25 or 30,000 lbs. Whether drafting a car or a big rig, it's just foolish. If the gory details bothered you, I'm sorry, it still bothers me having seen it after all these years.
     
  9. a priori

    a priori Canonus Curiosus

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    Thanks, Coot, for giving some first-hand comments and some additional warnings. I could go without the gory details, but I'm certain you would have preferred never to have had the experience yourself.

    Though drafting is nearly 30 years in the past for me, I think I am likely to follow trucks more than I had before. They do set a nice pace when addressing hills and having proper acceleration and deceleration. I won't follow at a 2 second interval, however. I think 3 or 4 is pretty good for me. I'm used to that spacing now, because it gives me time to adjust to activity ahead and avoid unnecessary braking and acceleration.
     
  10. Huntceet

    Huntceet Junior Member

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    What I'm riding is a recumbent tadpole trike. My head is maybe two feet above the pavement and i'm nearly prone. Get the picture? Nobody but another triker can draft me.

    Hunt
     
  11. darelldd

    darelldd Prius is our Gas Guzzler

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    Ha! Got me good. That's just cheating! ;)
    Of course I was totally thinking aero TT bike or somesuch. You're right. I'll shut up.
     
  12. darelldd

    darelldd Prius is our Gas Guzzler

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    With your obvious concern for the safety of others on the road... I'm wondering why more care isn't put into assuring that the tires don't come flying apart. I realize it is much cheaper (like saving gas by drafting) to recap tires. And it is much cheaper to run the tires until they fly apart instead of replacing them while they have some life and safety left in them. But are any of THESE considerations for other drivers taken into account by the truck drivers or the companies that own the trucks?

    You sure don't have to be drafting a truck to be severely injured or kiilled by a flying tire (or tire pieces). You can be on the other side of the highway!
     
  13. Chuck.

    Chuck. Former Honda Enzyte Driver

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    With diesel already over $4.00, truckers are going to have even more blowouts as they drive on a wing and a prayer.
     
  14. Kinare

    Kinare New Member

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    Sorry I have not responded to this thread, but work has been hellacious this past week. Thanks for all of the information here. After reading it, I really don't think drafting is a good idea. I get good MPG anyway (48ish but I drive 80% highway and driving under 70 here is suicide).

    I might try using the trucker as a pace car, as Bob suggested, but I wouldn't do it unless I were at least 4 seconds+ back. Any closer and it turns from better fuel economy to reckless stunt.

    As a side note, I saw a trucker blow a tire about two weeks ago. Started coming off in tiny fillaments and then BOOM the whole thing flew off and got shot into the air. I think that more than anything made me hesitate in the first place.
     
  15. johnson487682

    johnson487682 Junior Member

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    The only time I consider drafting a semi is when there's a strong headwind. This represents an increased air speed (which governs the length of the truck's displacement effect) with respect to the ground speed (which governs my and the truck's stopping distances). So, I can stay a safe distance behind the truck and still get some improvement in fuel economy. And, I need it just to maintain a "normal" mpg in a strong headwind.

    I generally stay 1.5 to 2 sec behind the semi, which allows me to see his mirrors (at 65-70 mph). If I drop back any farther, someone will pull in between us. I stay particularly alert on these rare occasions when I'm drafting, so I believe 2 sec is enough time for me to avoid any road hazards, and I'm sure I can stop faster than a big rig--even if it makes a panic stop. The argument about catching a piece of retread doesn't phase me, because I'm probably more likely to catch one when passing a truck as when following it--don't they usually get thrown sideways instead of straight back/under?

    There's one point about drafting that I haven't seen addressed yet in this thread: doesn't the semi's fuel economy get better if someone is drafting it? I once heard that the presence of a smaller vehicle near the point where the truck's air displacement collapses serves the same purpose as the small spoiler on the trunk of the Prius: it "trims" the airflow so that it collapses cleanly instead of forming eddies that pull on the truck.

    So, I am under the impression that drafting improves the fuel economy for both the drafter and the draftee. As long as a safe following distance is maintained, truckers should be in favor of it.

    Douglas
     
  16. Ichabod

    Ichabod Artist In Residence

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    Well I think the point is that to get those kind of gains for you and/or the trucker, you're entering reckless driving territory, and besides, the trucker won't know you're doing him a favor because if you're drafting for maximum effect, he won't be able to see you! :p You'll probably still get better MPG gains by slowing down a little.

    For me it's nice to know in an academic sense that you can increase fuel economy by drafting, but it's one of those things that to me just isn't worth increasing risk. People die in all kinds of ways in cars, and I find no thrill and no financial gain significant enough to increase my own risks.

    I used to be a terrible driver (you know, the kind who says "I'm totally in control, so it's ok for me to do crazy s**t and take stupid risks") and I still have to talk myself out of driving that way sometimes. I think I satisfy my speed-racer urges by making it a game to still outpace people who are weaving and driving aggressively, simply by practicing better long-term driving strategy.
     
  17. patsparks

    patsparks An Aussie perspective

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    Please don't take this the wrong way but you are not listening.
    Why would anyone want to?

    Where did you study physics? Remind me not to send my son there. They often don't get thrown back or sideways, just straight up and you drive into it. I wouldn't let it worry you. They are normally very light, just an inch thick strip of rubber 8 inches wide maybe 3 feet long with thousands of tiny steel wires sticking out all around, nothing to be scared of. And the stones the back tyres lift up are the special soft ones that don't damage paint or windscreens. What a wonderful world.
     
  18. a priori

    a priori Canonus Curiosus

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    Acknowledging that truckers don't care for tailgaters any more than do I, I still was interested in following up the "leads" on "research" into the benefits (lower MPGs) of drafting. At least one poster mentioned the Mythbusters' episode where they tested the hypothesis that a car would have less resistance and therefore higher mileage when drafting behind a big rig. Mythbusters did some wind tunnel testing and then tried it out on the road.

    It turns out there can be considerable savings (at least for one type of car behind a big, new rig), but the driver must be very close for the great benefit. Mythbusters said the safe distance was at least 150 feet behind the truck (going 55 mph). Many earlier posts here have shown that 100 feet is not a safe distance, but that is as far back as Mythbusters tested. (I don't understand why they didn't also test at 150 feet -- maybe because they knew there would be no significant effect?)

    Trailing 10 feet behind gave a nearly 40% increase in MPG, while falling back to 100 feet gave about an 11% increase in MPG. I'd love to go from 50 to 55+ MPG, but I don't think it is worth the risk.

    For a good review of the Mythbusters show (Episode 80), please follow this link to see the results of their tests.

    On the question of the truckers gaining efficiency by having persons draft behind them, there is much speculation on the internet. I think about the only thing people can agree on is that the truckers do not gain any measureable benefit (if any exists) from having someone "share" in their disturbed airspace. I can't imagine any trucker wanting to have this "benefit" given the tremendous risks to the following car(s) and the thought that the trucker could, possibly, be involved in a horrific accident.
     
  19. nomad

    nomad Junior Member

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    I did part-time (weekend hobby) local trucking for 1.5 years. Drafting did not bother me atall. But neither do dogs. Everybody is different. With some truckers you are getting into their personal space, others are not offended. If you wish to trail/draft a tail an over-tired and over-the-road truck(er), be my guest. I won't put my own or family's safety in jeopardy. As fuel cost rise and truckers (especially owner operators) try to cut costs, maintenance may suffer. Watch out for those "alligators" (flat tires)......

    PS: Truckers tailgate truckers too -- sometimes for drafting, sometimes?????


    Here is what some of the truckers as asking and saying (again, some of this post relates to truck on truck).

    Trucking Forums Message Board, Truck Drivers Forums
     
  20. a priori

    a priori Canonus Curiosus

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