The Orion hybrids—which are series hybrids, in which an engine powers a generator to power the electric drive motors— are gaining momentum in market. New York is the largest user, and Toronto and San Francisco have also placed orders. (Earlier post.)

The Orion VII buses with BAE HybriDrive combine a 5.9-liter, 260 hp (194 kW) Cummins ULSD (Ultra Low-Sulfur Diesel) engine with a 120 kW traction generator. The traction motor delivers 250 hp (186 kW) and 2,700 lb-ft (3,657 Nm) of low-end torque.

Regenerative braking recharges the lead acid batteries used for energy storage. The series hybrid design eliminates the transmission, removing a major maintenance item on vehicles operated in heavy stop-and-go conditions and eliminating the jarring shift points common among conventionally propelled buses.

Depending upon usage, the Orion hybrids deliver 25%–35% better fuel economy compared to conventional diesels. New York City transit reports average operational gains in fuel efficiency of 28%.

Emissions reductions are substantial: 90% less particulate matter, 40% less NOx, and 30% fewer greenhouse gases.

St. Louis Metro is the 39^th largest transit agency in the country, operating a total of 457 buses.

Orion Bus Industries is a subsidiary of DaimlerChrysler.