What if Highways Were Electric? Germany Is Testing the Idea.

An electrified highway is theoretically the most efficient way to eliminate truck emissions. But the political obstacles are daunting.

OBER-RAMSTADT, Germany — On a highway south of Frankfurt recently, Thomas Schmieder maneuvered his Scania tractor-trailer and its load of house paint into the far right lane. Then he flicked a switch you won’t find on most truck dashboards. Outside the cab a contraption started to unfold from the roof, looking like a clothes-drying rack with an upside-down sled welded to the top. As Mr. Schmieder continued driving, a video display showed the metal skids rising up and pushing gently against wires running overhead. The cab became very quiet as the diesel engine cut out and electric motors took over. The truck was still a truck, but now it was powered like many trains or street cars.