Does drafting on the highway improve gas mileage?

First of all, we want to start off by telling you to always follow at a safe distance on the highway. Don’t start tailgating school buses and semi-trucks across Canada and the United States after reading this article! Through this blog post, we are merely sharing some proven tips that hypermilers and fuel economy enthusiasts have been using with some success. Does drafting large vehicles on the highway actually improve gas mileage? Yes it does. Read on.


paceline of drafting cyclists drafting cyclists

Photo Credit: Mathieu Thouvenin                           Photo Credit: Eleaf


First of all, what is drafting?

Drafting or slipstreaming is a technique where two vehicles or other moving objects are aligned in close formation, reducing the overall effect of drag. The leader of the pack pushes the air, creating a slipstream or a wake of air that acts to pull the followers traveling behind. By exploiting the lead object’s slipstream, those following can save energy which makes it easier to maintain speed. When high speeds are involved, as in auto racing and cycling, drafting can significantly reduce the amount of energy required to maintain speed.


drafting in NASCAR auto racing

Photo Credit: Michael Napoleon

drafting or slipstreaming in Formula1 race

Photo Credit: nick@


Drafting a Big Rig

Let’s take this concept to everyday applications like driving down the highway. Here are some Mythbusters segments that tackled the question of whether or not drafting actually works!


Small-scale test


They did a small scale wind tunnel test to study the aerodynamics of a big rig. They captured video of smoke travelling over a miniature big rig and verified the low pressure area behind. They then stuck a miniature car to a force gauge to study the difference with and without drafting. The results:

– 7 car lengths: 21% drag reduction

– simulated 10ft: 60%

– simulated 6ft: 80%

– simulated 2ft: 93%


Full-scale test


After the initial test concluded that drafting was very likely to reduce drag, Freightliner lent the MythBusters their most aerodynamic big rig on the market to replicate the initial test in real life. A test engineer hooked up a computer to the fuel injection system to accurately measure the fuel consumption going 55mpg at various distances behind the big rig. The result of the test:

– 55mph control: 32mpg 

– 100ft: 35.5mpg, 11% improvement

– 50ft: 38.5mpg, 20%

– 20ft: 40.5mpg, 27%

– 10ft: 44.5mpg, 39%

– 2ft: 41mpg, 29%


The fuel economy actually dropped at 2ft due to the nervous throttle foot of the driver trying to maintain that 2ft gap.


Bonus test drafting a big rig on a bicycle

Bike Drafting


So can you draft safely?

Vancouver School Bus regularly provides transportation for organized tour groups. We often travel on the Trans-Canada Highway as well as the Interstate 5, running down the West Coast towards Seattle. Our drivers follow the speed limits and they try to drive as smoothly as possible both for a comfortable ride as well as good overall fuel economy. Remember to follow the safety tips in this blog post and to always be aware of the dangers of tailgating. Remember to avoid driving in the blind spot of trucks and be aware that 150ft is the minimum recommended following distance at 55mph. We don't mind if you hitch a ride on our slipstream if you want to use drafting as a way to reduce needless fuel consumption. Another hidden benefit is that you’ll never get a speeding ticket if you follow behind our buses!

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This entry was posted on Monday, July 23rd, 2012 at 5:49 pmand is filed under Company News. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

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