When the bay doors opened and the new electric bus rolled in during Mountain Line’s launch event on Thursday, there was a strange silence.
Despite the cavernous acoustics of the warehouse space, the bus moved forward with almost no sound — the gentle creak of fresh rubber on its tires louder than its electric propulsion. Even inside the bus, sitting right over the motor, there was not much to hear. Casual conversations — even whispers — were fully audible.
“It's so quiet,” said Mountain Line operation director Jim Wagner. “When we had students on board, this young lady that was sitting across from me, I could hear her tapping the phone.”
And yet, this peaceful quiet of the electric bus ride amounts to an afterthought, a bonus reduction in noise pollution alongside the bus’s greater reductions in carbon emissions.
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“Replacing one hybrid bus with an electric bus reduces the annual greenhouse gas emissions by 61 tons, which is the equivalent of removing 10 passenger cars on the road each year,” said Mountain Line CEO Heather Dalmolin. “When Mountain Line fully transitions to an all-electric fleet, we will reduce local annual greenhouse gas emissions by 68%.”
That’s Mountain Line’s goal, Dalmolin said, one that began in 2008 when Flagstaff voters overwhelmingly approved Proposition 401 to fund the purchase of electric buses.
“Fast forward 10 years and Mountain Line was the first transit system in the U.S. to operate a 100% hybrid-electric fleet,” Dalmolin said.
Now, they officially have two fully-electric buses that will be operating on the streets of Flagstaff by mid-April. The 444 kilo-watt-hour batteries provide each bus with a range of about 100-130 miles per charge, Wagner said. They have more powerful acceleration than the fleet’s current hybrid buses, and they’re also equipped with regenerative braking — a system that re-charges the battery while slowing the bus by converting the energy of the bus’s movement into stored battery power.
“For instance, when we went up Snowbowl Hill with one unit we used years ago, it used six units of power,” Wagner said. “And coming back down it gained four units of power because of the regenerative braking.”
The plan is to gradually replace the Mountain Line fleet with all-electric, zero-emission buses as their current hybrid-electric fleet reaches the end of their useful life — 15 years, according to Mountain Line communications director Jacki Lenners. As their newest hybrid bus was purchased in 2017, by 2032 Mountain Line hopes to have fully transitioned to a fully electric fleet.
“As long as we’re able to secure funding,” Lenners said.
Their funding strategy has been to use local tax dollars — such as those provided in 2008’s Proposition 401 — to bring in federal grants that require matching contributions. It’s worked so far. The purchase of their first two buses was made possible due to an award from the Federal Transit Authority (FTA), which has supported Mountain Line electrification efforts with over $82 million in grants since 2019.
And there’s more money out there.
“When President Biden signed the Bipartisan Infrastructure Law, it created an unprecedented opportunity for us to drastically improve the lives of millions who ride buses every single day,” said FTA deputy associate administrator Erica Maza. “This legislation provided $5.3 billion over five years in conforming with competitive grants.”
These first two electric buses represent “a significant step forward towards establishing a zero emission fleet that is safe, cleaner and more sustainable for the future of Flagstaff,” Maza said.
With this step behind them, Mountain Line’s full transition seems imminent.
“We are well on our way,” Dalmolin said. “Mountain Line is receiving federal grant money for an additional four zero emission buses along with electric support vehicles and the infrastructure to support the transition to electric.”
For utility provider and Mountain Line partner Arizona Public Service (APS), the new electric buses will serve as a vital research opportunity to gather data about the implementation of electric vehicle infrastructure around the state.
There are a lot of questions in need of answers, said APS strategic projects manger Judson Tillinghast. He’s curious to see how Mountain Line’s rollout will create insights about the frequency of recharging and the placement of charging stations, how charging schedules can take advantage of APS excess solar energy during daylight hours, and even how the buses might be able to re-supply power to the grid.
“We're just getting to the beginning of this, but everyone talks about the future of vehicle-to-grid constructs,” Tillinghast said. “Some of these buses claim to be capable of pushing power back out to the grid. So if there's excess battery capacity that hasn't been used during the core peak hours, you send a signal and dispatch that battery back to the grid, providing savings for everybody.”
As a utility provider, APS has promised to provide completely carbon electricity free by 2050, with a goal of reaching 65% clean energy by 2030. Their partnership with Mountain Line is a crucial piece of that goal, said senior public affairs manager Janet Dean.
“We're going to receive bus and battery performance data through this partnership,” Dean said. “That's going to allow us to shape policy and develop programs for fleet electrification in the public transit sector across the state.”
With Mountain Line paving the way, other bus fleets in Flagstaff are looking to follow suit. According to Flagstaff Unified School District (FUSD) superintendent Mike Penca, the school district has already transitioned to lower emission propane-fueled school buses.
While they have so far been unsuccessful in receiving grants for fully electric buses, “we’re continuing to apply,” Penca said. They hope to receive funding for both buses, other electric support vehicles and a transportation facility that will be able to support electric vehicle charging. These developments are “maybe 4-5 years down the road,” Penca said.
For FUSD bus driver David Spence — who said he would be very excited to drive an electric bus — another option could be diesel-to-electric conversion.
“You can take an old diesel bus and convert it to electric for $140,000,” Spence said. “That’s what I’d advocate for.”
Northern Arizona University also has a “strong desire” to electrify their bus fleet, said Erin Stam, director of university transit services.
“It’s a challenge, because we’ve been told we’re not public transit,” Stam said — a designation that disqualifies them from many types of grant funding. University transit services are also a self-funded, auxiliary department to the university itself, and thus not able to dip into tuition funding. Nonetheless, NAU president José Luis Cruz Rivera is “highly motivated to meet our sustainability goals,” Stam said.
Altogether, electric buses and other electric vehicles will be an important part of Flagstaff’s future, said city councilmember and Mountain Line board member Miranda Sweet.
“The goals of the city are set forth in our carbon neutrality plan,” Sweet said. “These benchmarks will not be attained without a robust transit network served by zero emission vehicles. Today, we start making these goals a reality.”