In June, Siemens announced a partnership with Swedish transit authorities for the second pilot study of a new way to electrify highway freight shipping.
Well, it’s sort of new—dubbed eHighway, the system powers trucks through overhead wires transmitted to moving vehicles, a method that has worked for streetcars for more than a century.
eHighway is one of the only currently viable possibilities for electrification of freight trucking. Though freight trucks are similar in weight to the all-electric buses already in operation, trucks face several specific hurdles to electrification. Batteries’ weight would cut directly into trucks’ profitability, and so would stopping to charge. Even as battery costs decline, neither of those limiting factors will change.
Martin Birkner, head of the eHighway project, says that despite those obstacles, a number of broader factors make electrified trucking worth pursuing. While trains have an edge in efficiency, trucks are far more flexible. And in some areas, much of Sweden included, rail infrastructure is already at or near maximum capacity, a situation that will become more common as global shipping volumes grow.
By partially electrifying existing highways, eHighway could balance the flexibility of trucks and the efficiency of trains. Trucks in the Swedish demonstration, like those in a demonstration route already operating outside of Los Angeles, will be electric-fossil fuel hybrids. They can connect to the electrified lines along main routes, then disconnect and reach their final destinations on diesel power.
The connections and disconnections are performed at full speed, using a specially engineered version of the familiar overhead connector. Modern versions are already in use on everything from buses to light rail to mine trucks.
“This is an absolutely proven technology,” says Birkner. “We didn’t have to reinvent the wheel.” In fact, the overhead-wire system was pioneered by Siemens’ founder, Werner von Siemens, in 1879.
Birkner says that while the demonstration trucks are hybrids, the end goal is a system of fully electric trucks with relatively small batteries for last-mile travel. Though such systems could eventually have a big impact on CO2 emissions as renewable energy expands, the more immediate impact would be on local air quality, particularly near high-traffic areas like ports.
Demand for such systems may be driven by local regulation and policy goals, such as Sweden’s goal of achieving a zero-emissions transit fleet by 2030. The consulting group Gladstein, Neandross and Associates, however, did conclude that for short-range operation, such as near ports, electrified trucks could actually be cheaper to operate than their diesel siblings—particularly where the cost of gasoline is highest relative to the cost of grid electricity.
The infrastructure itself is another matter—Birkner says the cost of installation could vary widely, and bodies considering the systems haven’t yet settled on funding models. The Swedish test system will be installed by summer 2016, and that question will be explored, along with system performance, during the two-year test period.
Sign up for Data Sheet, Fortune’s daily newsletter about the business of technology.