The move forward to a green transportation future could involve a step back into the past. In the early years of the last century, overhead wires above city streets supplied power to electric streetcars and trolleys. That same principle could be applied to modern electric trucks on major highways. The United Kingdom is installing overhead contact lines for that purpose on a 12.4-mile section of motorway, with the pilot project serving as a testbed to see if the scheme could be rolled out nationwide.
The technology, by Siemens, is called eHighway. An active pantograph on the roof of the truck can move to maintain contact with the overhead wires and works at highway speeds. The trucks themselves feature a hybrid drive system, so they don't have to maintain constant contact with the power lines. They can change lanes to overtake another vehicle, for instance, and the contact lines don't have to be strung above complex interchanges. More important, onboard batteries allow the trucks to do the non-highway part of their journey, with Siemens claiming that in Germany the off-highway portion of truck trips is 50 km (31 miles) or less in 89% of cases. The batteries, therefore, can be much smaller than in full-EV trucks that solely use battery power. Another advantage is that there's no downtime due to recharging.
The UK test follows installations in Germany, Switzerland, and the United States. The U.S. section is on a one-mile stretch of road in Carson, California. As to a more meaningful rollout, Siemens claims that, in Germany at least, overhead contact lines could be added to 300 miles of highway (both directions) per year.