A new report and recommendation released by Seattle’s King County Executive Dow Constantine shows how Metro Transit could completely transition the bus fleet to zero-emission powered by renewable energy between 2034 and 2040.

The move would reduce greenhouse gas emissions and improve local air quality and public health — key goals outlined in King County’s strategic plans on climate and social justice. Battery-electric buses cost incrementally more than hybrid diesel-electric buses, but have reduced long-term maintenance costs as well as health and environmental benefits, according to the agency.

“We have the opportunity to further cut pollution and improve the quality of life for our region,” said Metro Transit GM Rob Gannon. “We are encouraging the bus manufacturing industry to continue to improve the technology and drive down costs so we can accomplish these goals.”

A successful transition will depend on a number of conditions being met over the years ahead, including advancements in bus technology, development of charging infrastructure, and affordability.

Metro currently operates about 1,400 buses — a fleet with a mixture of diesel, diesel-electric hybrids, electric trolley, and battery-electric buses. Metro was the first transit agency to adopt diesel-electric hybrid buses.

In January, Metro announced its commitment to purchase 120 battery-electric buses by 2020. That announcement also put Metro in the lead position in committing to battery-electric buses.

Transitioning Metro to zero-emission will require further bus manufacturer advances, including further development of 60-foot-long articulated battery buses, long-range buses and standardized charging stations. Once the industry addresses range and size requirements, Metro could achieve a zero-emission fleet through ongoing fleet replacement and expansion.

Cost estimates spanning through the year 2047 are included in the report and outline a conceptual Metro fleet mix of 40-foot and 60-foot-long battery-electric buses with short- and long-range travel and charging capabilities. Battery-electric bus purchases and maintenance are estimated to cost 6% higher than diesel-electric hybrid buses; however that estimated figure is reduced to 2% higher than diesel-hybrid buses once the benefits of reducing pollution and noise are factored in.

A zero-emission fleet powered by renewable energy could reduce GHG emissions by 80%, up to 1.8 million tons of carbon emissions by 2047, eliminate air pollutant tailpipe emissions, and reduce noise, improving the public health and quality of life for all King County residents.

Metro, manufacturers and other transit agencies are monitoring the ongoing performance of emerging battery-electric bus technology and vehicle prices. Long-term maintenance costs will be better understood as the industry matures and technology improves.

The report prioritizes deployment of new zero-emission buses on service operating from South King County, improving air quality and public health first in low-income and minority communities, which are most vulnerable to the public health impacts of air pollution.