Because they cover significantly more mileage than the average passenger car, with much worse fuel economy, large commercial trucks are a major source of emissions.
Last year, Volvo Trucks aimed to address this issue with a concept truck that demonstrated ways to improve fuel efficiency through aerodynamics and weight reduction.
Volvo Trucks sells large commercial vehicles under the same name and logo as Volvo Cars, but is actually an entirely separate entity.
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Now, the Swedish firm has fitted the concept truck with a prototype hybrid powertrain.
The system recovers energy when the vehicle is driving downhill or braking, and uses it to enable all-electric driving on flat roads or low gradients, Volvo Trucks said in a press release.
It claims the concept is capable of 10 kilometers (6.2 miles) of all-electric driving.
The company previously said the concept truck's aerodynamic improvements and weight reduction allowed for fuel savings of 30 percent over a conventional truck.
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The concept is also fitted with a hybrid-specific version of Volvo's I-See driver-assist system, which analyzes upcoming topography using GPS data and digital maps.
Software determines the most efficient use of both the diesel engine and electric motor based on the terrain, as well as the optimal times for energy recovery, Volvo says.
Aerodynamic modifications include chassis side skirts on the tractor, fairings covering all but the front set of wheels, and spoilers on the back of the trailer.
Volvo also replaced the side-view mirrors with cameras, something Tesla and other automakers have unsuccessfully lobbied to make legal in the U.S.
Altogether, the changes improve aerodynamic efficiency by 40 percent over a conventional truck, Volvo previously said.
Work on the concept began in 2011, and the truck began testing in the fall of 2015.
The truck itself won't go into production, but Volvo says some of its aerodynamic elements are being incorporated into the vehicles it actually sells.
Development work on the concept truck will continue, with the ultimate goal of reducing fuel consumption by 50 percent over a conventional truck.