Aerodynamics for tractor trailers is all about reducing drag caused by air flow around the vehicle. And the reason for that drag reduction is to save money by reducing fuel consumption. Whenever we lower fuel use we get the added benefit of lowering greenhouse gas (GHG) emissions.
In 2011, Transport Canada asked the National Research Council to assess several aerodynamic strategies for drag reduction on heavy trucks and intercity buses. That study produced interesting findings. Its report is called Review of Aerodynamic Drag Reduction Devices for Heavy Trucks and Buses. It’s available from Transport Canada.
Much research has been conducted in wind tunnel tests around the world using large scale models of actual tractors and trailers.
Drag Increases in Cold Weather
One particularly important fact from these studies found that colder climates like Canadian winters and those in Northern US increase drag on vehicles because the air is denser. In fact testing found that at 0 degrees Celsius (32F) aerodynamic drag is nearly 20% greater and fuel consumption 10% greater, stressing the need for adding aerodynamics to offset.
That means if you drive at 65 mph and your truck in summers gets 6.5 mpg US, in winter under similar conditions but with cold temperatures your truck without adding aerodynamics would only get 5.85 mpg.
So 30,000 miles of driving in winter would cost an extra $1,282 in fuel at $2.50 per gallon. As the fuel price rises, so does your additional cost. At $3.00 per gallon it costs you $1,539 extra due to cold weather.
It’s important to keep in mind aerodynamics don’t just work in winter, they provide savings year round.
Truck and Trailer Manufacturers
Manufacturers have taken a good look at aerodynamics. They’ve narrowed the gap between tractor and trailer to smooth out airflow along the sides. And streamlined tractors are everywhere these days. Trailers are being built lighter and reefer units nowadays have rounded edges to reduce drag.
Those improvements are great and they do reduce fuel consumption. But the purpose of this post is to provide you with an opportunity to add easily installed aerodynamic devices that will not cost an arm and a leg and will still enable your vehicle to perform properly and profitably.
Trailer Side Skirts
A notorious source of drag caused by air turbulence is the trailer underbody. A 2012 study of adding trailer side skirts noted average fuel savings of 5%. If your truck runs 100,000 miles per year and gets 6.5 mpg and fuel costs $2.50 per US gallon and you save 5% = $1,925 less fuel spending per year. Multiply that by the number of trucks in your fleet and you’ll see serious savings.
Trailer skirts also reduce hazardous tire spray and drivers report better stability in crosswinds. The payback period for side skirts is said to be ten to eighteen months.
Add a Boat Tail Fairing
Wind tunnel tests of using a boat tail fairing on the rear of a trailer fitted with side skirts boosted overall fuel savings to 9%. That’s a savings of $3,176 on the 6.5 mpg truck now reaching 7.085 miles per US gallon.
A two man crew can install one in about an hour.
Other Aerodynamic Add-ons
Some estimates say adding wheel covers reduce air drag by 3%. And turbulence can be further cut by installing slotted mud flaps that allow air to flow through but stop stones and other debris.
Low Rolling Resistance Tires
Low Rolling Resistance Tires are designed and manufactured with less tread and simpler tread patterns to make them roll easier. They reduce the resistance caused by tires rolling on a road. They require less effort to roll, thereby saving fuel.
They typically cost more than standard tires and don’t last as long due to their design. But fleets like them because tire life can be extended through low rolling resistance retreading for use on drive or trailer axles for the life of the casing. And this type of retreading still delivers fuel savings.
If you’re not using add-on aerodynamics we hope you’ll consider it and stop buying more fuel than you need.
At BrightOrder we’re all about saving money for your fleet or maintenance/repair shop.