New Electric Bus Could Travel 350 Miles Per ChargeThat's longer than nearly every U.S. mass transit route, its maker says.

Electric bus startup Proterra, whose early models are already accepting passengers on the streets of Philadelphia and a few other U.S. cities, yesterdayunveiled a new designthat it claims will travel up to 350 miles on a single charge.

That's longer than nearly every municipal bus route in America, which theoretically positions the new bus as a viable replacement for fossil-fueled public transit. There are a lot of caveats, not the least of which is price: the bus, called the Catalyst E2, is likely to be significantly more expensive than its diesel brethren. That would make it unattractive to perennially cash-strapped transit agencies.

Still, the electric drivetrain's reduced maintenance costs will help offset the purchase price, and there's no denying that the ability to travel hundreds of miles on a single charge is a game changer. It's also a feat that most electric bus makers have shied away from as they unveil concepts packed withself-driving technologyand features likewireless phone chargingthat boost passenger comfort.

Proterra, founded in 2004 by clean transit veteran Dale Hill, is different. The Catalyst E2, whose prototype already travelled 600 miles on a single charge during a test run last month, would join two other all-electric models already in production. Philadelphia's transit agency has among the largest fleet, with 25 Catalyst FC models that travel up to 62 miles per charge.

They're also on the road in Worcester, Mass., whose transit agency says their batteries and drivetrains have taken major Northeast snowstorms in stride. Nationwide, Proterra's busses have travelled 2.5 million miles in revenue service.

Proterra didn't offer a timeline of when the Catalyst E2 would go into production.