When thinking of Los Angeles, clean air and double-decker buses aren't the first things that come to mind.

Yet the city of angels will put the first all-electric double-decker bus into service later this year on the Foothill Transit's Silver Line route (or Silver Streak route, depending on which end you start from).

The route runs a little more than 35 miles from downtown L.A. to Montclair, in the east valley.

Alexander Dennis bus converted to electric power by Proterra for Foothill Transit in L.A.

Alexander Dennis bus converted to electric power by Proterra for Foothill Transit in L.A.

The double-decker Alexander Dennis bus that will run the route later this year will be outfitted with up to 600-kwh electric batteries by Proterra, the world's largest electric bus manufacturer.

"We’re seeing increasing global demand for electric buses that combine high passenger capacity and comfort,” said Robert Davey, president of Alexander Dennis, Inc. “With congestion and local air quality challenges remaining top of every transit authorities’ agenda, we’re excited to raise the bar in Los Angeles County."

Alexander Dennis says they are the largest manufacturer of double-decker buses in the world.

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Matt Horton, chief commercial officer of Proterra, says the double-decker bus will use the same battery and drivetrain as the buses Proterra builds itself. Proterra builds its own carbon-fiber buses, and drove one to a world record of 1,101.2 miles without recharging last September.

The double-decker hasn't been tested yet, so Horton was unable to give a solid range estimate but noted that most transit customers are interested in buses that will go 200 miles or more before needing to recharge. The Silver Streak runs 24 hours a day, every 15 minutes through the day, with six stops along the way, and every hour overnight.

Foothill Transit uses overhead charging stations—like street lights—for most of its electric fleet. The double-decker, however, will plug-in and take about six hours to charge on a large, 120-kw fast charger, says Horton. (It's too tall for the overhead charging stations.)

Proterra Catalyst electric bus

Proterra Catalyst electric bus

Foothill Transit has one of the largest electric bus fleets in North America and is one of several fleets aiming to go fully electric by 2030.

Transit fleets are among the first transportation segments to move to electric power on a large scale because fleet operators care most about bottom line operating expenses, where electricity is cheaper, said Simon Lonsdale, chief strategy officer with Chargepoint, which is focusing on building chargers for bus fleets.

Transit agencies are interested in double-decker buses because they can move more passengers in a smaller road footprint than running additional or articulated buses on existing lines, which can also compound traffic jams.

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“As congestion intensifies across Southern California, every inch of road space matters," Doran Barnes, executive director of Foothill Transit, said in a statement. "So increasing passenger occupancy while maintaining comfort and a singular bus footprint is a public transit solution we’re really excited to introduce.”

The Alexander Dennis double-decker bus seats 86, about as many passengers as could cram into a standard bus with many of them standing.

Passengers will have access to wi-fi and storage space on the bus.