Proterra recently announced its 40-foot, zero-emission Catalyst XR electric bus drove 258 miles on a single charge under test conditions at Michelin’s Laurens Proving Grounds (LPG). The Catalyst XR was able to achieve that mileage with eight battery packs, and predicts with ten packs, it could go up to 300 miles on a single charge. According to available General Transit Feed Specification (GTFS) data, most bus routes in the United States run less than 200 miles per day, which Proterra believes bring “most routes within reach” of the bus’ current technology.

The success of that technology, according to John Sleconich, Chief Engineer at Proterra, was made possible by composites.

“The purpose-driven Catalyst design affords the best efficiency rating ever for a 40-foot transit bus, at 22 MPG equivalent,” said Sleconich. “Proterra buses are the only mass transit vehicles built from the ground up as an electric vehicle. With a unique aerodynamic body made from carbon fiber and advanced composite materials, we are able to reduce mass for maximum efficiency.”

Since the bus is made with carbon fiber and other advanced composites, it is more durable than diesel and diesel-hybrid buses made of aluminum or steel. It also is more corrosion resistant and offers a greater power-to-weight ratio. According to Proterra’s Sept. 3 press release, 40-foot buses typically have a 12-year lifespan. The company adds that customers who choose a Proterra bus will “dramatically reduce maintenance costs, saving around $135K” per vehicle over that 12 year period.

Ryan Popple, Proterra CEO, adds that in addition to the performance benefits that result from composites manufacturing, the bus will also have significant environmental and economic impact. Back in June, Fortune called the Catalyst XR the “Tesla Model S of electric buses.”

“While diesel buses pollute our communities and are increasingly more costly to own and operate, Proterra is pushing the bounds of EV technology and steadily driving down costs,” said Popple. “Achieving this range is validation for our technology and gives us the confidence that Proterra is capable of what we initially set out to accomplish – replacing every fossil fuel bus in the United States with a fully electric one.”