Drafting for MPG - Some Thoughts

Just one more post and I am done.
from wiki:

Drafting or slipstreaming is a technique where two vehicles or other moving objects are caused to align in a close group reducing the overall effect of drag due to exploiting the lead object's [ame="http://en.wikipedia.org/wiki/Slipstream"]slipstream[/ame]. Especially when high speeds are involved, as in motor racing and cycling, drafting can significantly reduce the paceline's average energy expenditure required to maintain a certain speed and can also slightly reduce the energy expenditure of the lead vehicle or object.

To actually "draft" on the highway, you would need to be within a couple feet.
Yes, you can actually draft on a highway, but you would not be drafting if you can see
the trucks mirrors.
Criminal with being 2 cars distance from a truck....damn criminals are everywhere!

The OP I thought didnt make any sense, but I was adding my "thought" as the title suggested.

 

There is one fact seems no one mentioned here: Big trucks break much slower than small cars. So it is much safer to follow a big truck than to lead it.

 

Reaction times are a factor and if the truck slams into something in front of it the stopping distance is...ahem...reduced. Fatalities from submarining into the back of trucks is not unknown. Following too close the cause.

It's just not safe, don't do it.

 

You are bandying semantics. Have you actually monitored instant mpg while drafting and following a diesel big rig then moved away from the truck? You don't have to be super close to benefit from reduced drag. You can be 15 car lengths or more behind a large truck and still benefit from reduced drag. Any further and you are just benefiting from reduced speed.

 

If you have not figured it out yet, ProximalSuns simply loves to argue.

 

Do not!

Doh!

Not counting this one:

Mr. Incredible 5
ProximalSuns 5
F8L 3

 

Good thing I like you or I'd throw up the ban smilie. LOL

 

Are you sure that applies to all big trucks, including the empty and lightly loaded ones to good tires and brakes?

Remember that some trucks do pass the surprise equipment inspections.

 

Well, I wouldn't want to be tailgated by a semi, but semis blow tires, lose load and jack-knife so I wouldn't want to be following closely either.

Also remember that the people following you have to brake in time as well: the chain of fools makes driving more dangerous. (Which is another reason to leave a good buffer on a 2-lane road: you need to leave space so that your tailgaters can overtake you.)

At least if there's a semi following me the length and size means that there's probably only 1 vehicle to worry about. A good semi driver will leave a very large buffer because of the longer braking distance, but ignorant drivers are liable to fill it.

 

As tempting as it is to get behind a semi for some free MPGs I tend to avoid getting too close. One rock into your windshield and you just lost any potential fuel savings and then some. My comp. deductible is $250. That would buy a lot of gas. I've also seen semis drop debris or straddle it, leaving not much time to react.

 

I agree w/ crebble 100%. The benefits don't outweigh the risk.

 

I think the buffetting is a sign that your Prius is in the pocket.

My commute is up and down I-95 from NYC to Connecticut and back, and when the opportunity presents itself I'd saddle up 6-7 car lengths behind a big rig at 60-70mph. During this, my Prius would be buffetted by some turbulence coming off the square end of the big rig, but I'd see the instaneous MPG reading improve by 5-10 or so.

I would never dare use cruise control while doing this though!

 

you must live near me or in an area frighteningly similar. the freeways around here are so congested and full of aggressive drivers that safe driving becomes a real challenge. I've seen more accidents (several fatal) in the 7 mile stretch of freeway I drive on my commute than anyone should have to. people just have no regard for human life around here, at all.

oh, and the number of people I see weaving around in traffic at high speeds on cell phones with kids in the car is ridiculously high around here. frustrates me to no end.

 

I have a name for those people, I call them AAOTRs (like the heart artery). It stands for Another A$$hole On The Road!!! I live on Long Island and see them all the time.

I actually came up with an idea once, but never did it. It was to mount a paintball gun in the front grill. When someone cuts you off, you just press a button and "mark" their car!

 

I think people overreact when they see the word drafting. We've discussed this ad nauseum over the years and most people agree that they "draft" leaving a 3-5 second distance between themselves and the semi. That is quite far in today's traffic standards. Any more than that and other people will move into that spot. I have found that after about 3 seconds the drafting benefit is diminished greatly but the blocking affect is still there and you will get better gas mileage by slowing down thanks to the blocker.

Here are examples of a 3.5 to 4 second following distance.

 

I draft big trucks and I can not lie.
You other brothers can deny,
When a semi rolls by with an itty bitty pace
And good Mpg in yo face
You get sprung.

 

Actually the single axle trucks(bed & front integrated) have much poorer braking than semi-tractor trailers. Those small front tires have poor braking ability when on a single bed. I much prefer to draft the single beds.

Once we were behind a semi tractor trailer(not drafting) that suddenly locked all its brakes because of something in front of him. Tho we were only going 40mpg, it was very very easy to outbrake him.

 

That looks closer than 3 - 4 seconds when traveling @ 60 mph. I'm seeing 5 of the long dashed lines in the pictures, there may be 6 because of how you took the picture. If we assume 30 feet between strips, it would be somewhere between 150 - 180 feet, with you traveling 88 ft/sec. I'm guessing you are closer to 2 to 2.5 seconds behind.

Correct my bad assumptions as you see fit!