Volvo Tests Ultra-Efficient Plug-in Hybrid-Electric Diesel Bus

New plug-in hybrid diesel bus could slash fuel consumption up to 80 percent.

When it comes to the electrification of motorized transport, cars like the Tesla Model S, Nissan Leaf, and Chevrolet Volt have received the most attention. But the same technologies are also being put to use in much larger vehicles.

Volvo is testing a new plug-in electric hybrid diesel bus in Gothenburg, Sweden. The company says the vehicles can cut fuel consumption and carbon-dioxide emissions by 75 to 80 percent compared with conventional buses. And if the buses are fueled with biodiesel, carbon-dioxide emissions would be cut by 90 percent.

Increasing the fuel efficiency for buses and trucks is an easy way to cut fuel consumption and greenhouse-gas emissions, mostly because these vehicles get such terrible mileage to begin with. New York’s old diesel buses got about 2.75 miles per gallon. So even if the MTA’s new hybrid buses only get 4 mpg that’s almost a 50 percent improvement. (The MTA says is has about 800 hybrid buses on the road, with more to come.) When you’re dealing with mass transit, marginal gains in efficiency go a long way. And because cash-strapped transit agencies often keep old diesel buses running for years, those gains come relatively easily. Of course, the most effective way to lower emissions, per passenger mile, is to get more people on the bus. The average bus in the U.S. has only about a quarter of its seats full.

Volvo has been producing hybrid buses for several years. But the plug-in technology represents a new wrinkle, enabling the bus to drive several miles on battery-powered electricity alone. Buses that run short, defined routes can recharge at the end of each journey relatively quickly, thus running most of the day on electricity.