Large semi-trucks employing conductive technology can cruise along in the right lane of a 1.2-mile stretch of the E16 highway outside the city of Gävle, close to the Baltic Sea in central Sweden, using electric power.

Called the eHighway, when the big rigs exit the test area they automatically revert to their diesel plug-in hybrid powertrain fueled by bio diesel.

Or, they can travel up to two miles on the stored electric energy of a fully charged five-kilowatt hour lithium-ion battery.

Similar to the overhead power supply for light rail, an energy collecting device called a pantograph mounted behind the cab, raises to connect with the overhead wires about 18 feet above the roadway.

The system feeds 750 volts DC to the pantograph, which is connected to the truck’s electric hybrid system.

Developed by tech giant Siemens, the pantograph technology is not new, and is based on 120-year-old tram technology.

What makes it innovative is the hybrid technology that can “seamlessly” switch from one power source to another.

Should a driver need to pass a vehicle, the pantograph will disconnect from the overhead wires and lower, then it reconnects when the pass is completed.

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The Volkswagen-owned Scania parallel hybrid trucks are normally powered by a 360 horsepower 9.0-liter diesel engine that runs on bio diesel.

Electric motivation is provided by a 130-kilowatt electric motor.

The eHighway is a collaboration between Region Gävleborg (the regional authority), with funding from the Swedish Government, technology firm Siemens and truckmaker Scania.

While the project is a two-year test to see how the system performs under normal traffic conditions and different weather conditions, it’s seen as a key component in achieving Sweden’s ambition of a fossil-free heavy-duty truck fleet by 2030.

Siemens is currently constructing a similar section of roadway in California in collaboration with the Volvo Group. This will be two miles long and is due to open by the end of the year.