Drafting Behind A Vehicle To Improve Fuel Efficiency?

Before a few days I watched this episode on mythbusters. They confirmed that drafting behind a big rig indeed improves car fuel efficiency, in some cases as much as by 40% (at dangerously close range).

They just tested different ranges behind the same truck. I wish they would have tested the following.

1. What happens if you are drafting behind a smaller truck? A car?

2. What happens if you are not exactly behind, if you are somewhere behind and to one side? Behind blind spot?

I am sure it is possible to take advantage of this drafting effect with some safety margin. I think everybody at one time or another has wondered about this effect or experienced it. Mythbusters just put numbers in there.

We always see migratory birds flying in the sky in a particular formation, something like a V formation. This is precisely for the same reason. The birds behind take advantage of the turbulence created by wind flapping of the bird ahead. Here is some in depth explanation of the bird formation. A group of fighter airplanes also uses such kind of formation to save some fuel on long trips. Often bicyclists and marathon runners can be seen running in formations to exploit the same advantage.

I am pretty sure the drafting effect works for quite some distance. So next time if you have a choice to drive through a lane which is empty ahead, or drive behind someone (at safe distance of course), choose the second one. You can comfortably get 5-10% efficiency boost with all safety precautions. Let us calculate what that means in terms of money. Say your vehicle original efficiency jumps from 30 MPG to 32 MPG (a modest 6.6% increase possible at very safe distance), then for every 960 miles, you will consume 30 galons instead of 32 galons. So after the cost of gas + taxes on gas , you are looking at somewhere around 6 to 7 dollars of saving. So if you drive 16000 miles a year, then it comes to around 100$ saving per year. So you are smiling. And mother earth is smiling too, because your gas consumption is around 30-40 gallon lesser, that means your CO2 emission is around 600 – 800 lbs lesser.

And 5-10% drafting advantage is at “officially safer” distance of 150 feet or more. A little less distance could be even more efficient. Even though we drive with vehicle distances less than 150 feet all the time, we should not endorse it officially, can we ?

If done safely and effectively for automobiles, this could indeed result in teamwork of cars to save fuel.

~ by Kedar on January 8, 2008.