Safer Drafting?
 

Well as its been said and proven so many times, drafting is an effective way to increase mpg. However it is very dangerous in everyday driving because of the close proximity you have to get in order to get effective gains.

In my driving however I have begun to notice that I get incredible FE gains when a tractor trailer passes me, even if for a moment. SO for the past couple of days I have done another non scientific experiment.

I began drafting the truck from the other lane. In other words, I stay one lane over and still maintain the 20-30 ft distance behind the rig. This keeps me off his ass and in his mirrors, so if he has to get over into my lane I just let up and let him and wait for the next truck.

As far as gains, my normal FE on hwy is roughly 47.5mpg, while side drafting it jumps to a whoping 58mpg+, I saw a steady high today of 67mpg on the scangauge.

So while not as dangerous, I see potential in this because apparently the broken air off the back of one of these monsters is about three lanes wide. So have fun trying it, just figured I'd share my results so far. Now good luck finding a trucker doing 60mph on a freeway.

I've heard this referred to as a surf draft. It is obviously beneficial and safer than following directly behind the truck. The downside of course is that your essentially creating a two lane road block while cruising. As usual, its hard to find them going as fast as you're willing to go. :)

my best "safe drafting" technique so far has been my CB. some drivers are really cool about it (i think it gives them a little better mpg too). some aren't, and a cb is a good way to find out so you can avoid them.

i haven't tried "surf draft" yet, sounds a lot safer.

In cycling, drafting like that with a cross wind would be called an echelon. Fortunately bicycle wheels can't penetrate a windshield like truck wheels can if they come off.

Because not many bicycles have windshields?

However, if you stop to think about the mechanics of a truck wheel coming off (a pretty rare thing), or the more common tread delamination or blowout, it would seem that directly behind the truck is going to be one of the safer places. If a wheel came off, it A) would have some outward momentum from wobbling against the lug bolts; and B) unless it was on the rearmost axle, would hit the wheel behind and bounce away to the side.

jamesqf, and I wish it were a lot more rare. I'm familiar with 2 fatalities during a relatively short time period that were caused by lost truck wheels on a local section of freeway (QEW) that I frequently travel.

google ["truck tire" died windshield] or something along those lines.

Your post seems critical of mine. Am I wrong to mention safety considerations?

I saw the same thing in town on a 18 wheeler. The wheel came off at about 30 mph.

Drafting is a great way to save gas and remember that its not just tractor trailors that you can draft. If you are in an economy car you can draft just about anything.

well driving is a risk no matter how you look at it.. your driving on a road with hundreds of other multi-ton objects traveling at 1/10 the speed of sound.. and many are piloted by MORONS.. Ill hide behind a 80,000lb semi and enjoy the added security of a added large brick wall like buffer against oncomming traffic and some added FE gain.. and risk a tire flying off.

Yeah those SUV's and vans make great cars to draft behind. however a semi allows you to follow further back and add some distance for safety.

Well said - distant draft only, for safety. I choose to draft no closer than 3 seconds, and that still gives a 10%+ benefit. Of course, that requires a truck going as slow as I want to, which is rare.

Also, faster traffic from the rear will pass without even a second look at you.

I've no doubt that it can and does happen. The question, though, is where the cars were that got hit, relative to the truck that lost the wheel. Were they directly behind (drafting, IOW), or off to one side? As I said, just thinking of how things might bounce around, it seems that directly behind would be safer than behind and off to the side.

Of course not. I'm just questioning the assumption that directly behind is the least safe spot. I think - and I admit it's just an opinion - that taking everything into consideration, in many situations I am in fact safer behind (though not TOO close to) a semi.

I haven't tried the "surf drafting" yet as most of the highways I traverse are either "trucks stay right except to pass" or are 2 lane only in one direction which creates a complete road block if doing the above.

When I'm on the highway though, I generally can sit about 40 feet behind a truck (well within my opinion of a safe distance (10ft per 10mph, doing 55, close enough). I jump from 36mpg to an incredible 47-50mpg when drafting and most truckers don't seem to mind, I generally try to gauge by whether they are speeding up to give themselves more distance or if they slow down, etc. You can generally tell how they feel by watching how they react when you "engage" on their draft.

I hava thought about the CB idea, but how do you identify whatever truck you're trying to get a hold of?

Any draft is a draft, whether you're behind a tractor-trailer or a Honda Fit, although perhaps tailgating Basjoos' Aerocivic would be a capital waste of effort.

A close-coupled tailgater is doing the lead vehicle a small favor by acting as the lead's new tail. Following closely, the tail vehicle gets less nose drag because that's the lead's problem, and the lead gets less tail drag because that's the tail's problem. Be that as it may, when another vehicle gets too close, I back off the throttle until they get fed up and pass. I don't want anyone closer than fifty feet or so, and that's my absolute minimum.

I don't like cuddling up too close behind a rig not because of the potential risk of flying delaminations but because I can't see anything else. Part of being an alert defensive driver is knowing what's going on ahead of me. I don't want to rely on the juggernaut's inertia to act as my buffer zone, that means that in the event of an emergency, I might wind up driving over somebody's mangled body. The truck will probably be what kills them, but still - I weave to avoid flat squirrels, I sure as heck don't want to hit a person, mangled or otherwise.

So dropping back a second or so behind a regular car gives me some palpable results and still allows me a long view down the road. Now, if only I could find a fellow hypermiler that's doing the same pokey 55mph that I'm doing. Seems to me that everyone out there is in one heckuva hurry and that 55mph speed limit is a lower limit, not an upper limit.

I've seen tires break in front of me. Last week I had to head for the ditch as a piece of rubber i'm pretty sure was larger then me flew at me. The transport behind me followed me to the shoulder. I was directly behind the transport but far enough back I had time to react, and get around the flying obstacle.

As for the poster who claimed that 'driving isn't safe anyways': The odds of me dying on the highway in my lifetime is 1:5000. I have a better chance of dying on the road, then dying due to the top five killer dieses including various cancers, heart diesease, and a few others. I'll do anything reasonable to increase those odds in my favor, like maintaining my vehicles safety systems, and driving in the safest manor i can.

And you should too. Every year, people die on the highways for no better reason then that they thought it would never happen to them.

I experimented with some close (<1 sec) tractor drafting last month on two separate occasions for over an hour. Safety concerns aside, it's not difficult from a purely technical aspect, but from my tank calculations (no Scanguage), <1 second drafting at 60-65 mph doesn't provide appreciably better mileage--at least on my Taurus--than does cruising at 50 mph. In fact, I suspect the extra heft needed to maintain the draft canceled out the resistance benefits. When you add the safety considerations mentioned in this thread, it doesn't seem worth it. I won't be doing it again. Long drives are much more enjoyable when I'm not constantly matching my speed to that of a vehicle ahead of me.

I find that drafting a semi around here (Toronto/Mississauga) is actually safer than you might think. My reasoning goes like this:

1 - Semis always leave a long space between them and the vehicle ahead

2 - Even my crappy car without ABS can break in a shorter distance

So, the space they have ahead provides a steadier speed than vehicles around you because it absorbs the rubber band effect, even when traffic gets more congested. Holding a steady speed and slow breaking of the rig or just working through the gears means that you'll rarely have to use the brake unless traffic comes to a complete halt or the rig engages in an emergency maneuver that involves locking the brakes. Even if the latter happens a smaller vehicle, especially if outfitted with ABS can still avoid a collision if the driver knows what s/he's doing and is paying attention to the road. In fact for this to work the driver must not lose focus and if s/he feels that is happening s/he should break off ASAP and resume normal driving.

Yes, it is dangerous but not absurdly dangerous if you are responsible enough to drive within your limits and the limits imposed by the traffic conditions. You need to use your best judgement to call it off or not even attempt it if there is any doubt about safety. There's a time and place for everything.

You can almost universally contact a trucker by the description of his truck and/or the mile marker/highway you're on.

Almost all trailers have numbers on the back of them, huge, easy to identify. The truck might also have a company name on the side, different from that on the trailer. Check that you can identify the type/brand/make of the truck that's being contacted. Refer to truck numbers (different from trailer numbers). Something will usually catch their attention, or you're on the wrong channel.

Regardless of whether you can see a personal name printed on the truck's door/side/anything, DO NOT use it on public broadcast. You might get run over.

That sounds good until the truck your drafting swerves around the accident that kills you.

That really doesn't deserve attention, but I'm bored....

Semi's CAN'T swerve around something fast enough that a driver (even one seemingly attached to his ass-end) can't react before hitting whatever the truck swerved around.

What that means: Even if you're attached nose to tail with a trucker, and he needs to swerve, the amount of time he'll need to successfully maneuver around an accident or the like will inevitably provide you with "sight time" enough to proceed in the same manner. If it didn't, the driver of the truck would inevitably hit whatever obstacle was in the road.

There is a very distinct appearance to a truck that is swerving, versus one swaying or anything else... any driver who can tail one that closely, would probably have learned to react based on the demeanor of the truck in front of him, as a matter of not being able to see in front, which also says that you wouldn't necessarily need to see the obstacle in order to know it was present and how to avoid it.

There is a given problem with tailgating a truck of that size though - he may not swerve for something that is still large enough to damage your vehicle intensely, like large rocks or medium animals, "gators" (tire treads), and other smaller obstacles. Draft at your own risk.

I can hardly imagine driving and having 50 feet of empty air between cars. Either it's 3 AM and nobody's out or traffic's too thick. I only draft truckers for short periods. Usually they're going too slow and I'd rather use more gas than fall asleep at the wheel. When they are moving along, I still don't like to draft for very long. I'm not much concerned about the safety aspect, more that I don't want to piss off a trucker that doesn't deserve it. I'd rather die on the road than of the cancer or alzheimers that run in the family. Not that I'd stick around long enough after diagnosis to let either one of those run its course.

Tractor-trailer wheels are not the same as car wheels. With split rim truck/trailer wheels it isn't the actual wheel coming off that is the danger, but the very heavy steel retaining ring that blows off that is so dangerous - and it isn't that uncommon. Frankly, I've never seen a trailer wheel come off (except in pieces) but I have often seen wheels that have blown apart with the ring acting as a projectile. After years of being in a truck-driving family and seeing what these things can do I never stay anywhere near the wheels of trucks on the highway.

This is interesting to me. Lots of ecomodders do aeromods to their cars that will get them a 0.002% increase in fuel mileage and be happy they did something. But when it comes to the largest possible aerodynamic benefit the bar suddenly becomes much much higher when following vehicles on the highway.

I can't say I believe in "drafting" per say. I would loosely define that as being engulfed in the turbulent air. Open windows exhibit an alternating crosswind from the other vehicles wake and sometimes you can close in on the vehicle you are following without using your gas pedal :eek:

I just practice following people. I never want to be alone... or the leader in a pack of cars if possible. This idea nets me considerable gains. Not very scientific, but I have seen approx. 2 mpg differences when not being able to follow another car. Even if it's only a 5% difference when following another car with an assured clear distance, I'll take that all day since it costs nothing to try and just be behind another vehicle (truck or not). :thumbup:

Point well taken, but I don't think there are many trucks on the road that use split rims anymore. They stopped producing those many years ago.

So, anyone else see any gains from side drafting?

I sure have seen benefits from "side drafting" an 18 wheeler. That's my preferred method on the interstate. I just monitor the conditions around me and move aside for other vehicles as needed. Unfortunately, the vast majority of my driving is on two lane highways... if the 18 wheeler is heading in the wrong direction, the draft kinda sucks!

RE 18 wheeler tires coming apart: When I was in college, I was making a trip home one night. I was pulling up to pass this 18 wheeler on a two lane highway when I suddenly heard a huge BOOM! The rest seemed to happen in slow motion. First, a couple chunks of tire came off. Then a huge strip of full width tread peeled away and is coming directly at me (the driver's side rear-most tire had blown). I stomped the brakes and swerved toward the shoulder. The tread flipped up and a little sideways as it came off, and as I'm passing next to it, it stood a little higher than my car. During all this, the trucker slams on his brakes, engulfing me in a cloud of burnt rubber smoke, raining what I can only guess was the remaining bits of tire sidewall all over me. I pulled over into a gas station a couple hundred yards up the road and had a serious case of the shakes.
At any rate, from what I could see, there is no safe place to be when one of those big tires blows.

Many people bring up how dangerous is it to draft, especially a big truck. Where I drive, there is lots of semi truck traffic, it cannot be avoided. So I make the most of it, drafting at a safe distance behind. Still some idiot insists on getting in there from time to time. The bottom line it driving is dangerous. Trucks add to this. I think as a group hypermilers drive better than most. Be careful out there!!!