Tesla’s Model S made news recently by offering a range that topped the 300-mile mark. Proterra’s bus has that beat by a factor of two. The company’s new Catalyst E2 series bus notched a 603-mile run at a Michigan proving ground last month, more than doubling the range of the company’s previous model. Proterra sells its $740,000 buses to municipalities. The E2 made its debut Monday at the annual meeting of the American Public Transit Association in Los Angeles.

A 600-mile passenger-free track run translates to around 350 miles of continuous real world bus driving, says Proterra CEO Ryan Popple. And that’s precisely the target Proterra was trying to hit. “We learned that for some cities there was a real need for buses that could do routes of 350 miles without recharging,” says Popple, a former senior director of finance at Tesla. He added that Proterra engineers achieved the benchmark by both reducing bus weight through the use of carbon fiber and improving the energy density of the vehicle’s battery packs.

Over the past five years, 35 cities have ordered 312 vehicles from Silicon Valley-based Proterra, and Popple says the first 34 E2 models will go to the Foothill TransitAuthority in Los Angeles county, with Reno, Nev., and 11 other cities following suit.

Among Proterra’s competitors are Chinese company BYD, which is on track to deliver 300 buses this year to a range of California cities including Lancaster and Palmdale. BYD opened a manufacturing plant in 2013 just north of Los Angeles to produce its buses, which have a real-world range of between 160 and 200 miles.

By transitioning to electric buses, cities are able to move away from diesel-powered vehicles that can be challenging in terms of emissions standards. Volkswagen engineers are being indicted for having created software that allowed the company’s diesel-powered passenger vehicles to pass U.S. emissions tests when they otherwise would have failed.