King County Metro Transit will begin testing long-range, battery-powered buses that can travel more than 140 miles on a single charge.

The buses will be tested on longer routes that include steep hills. If the test is successful, the buses could be used on around 70 percent of Metro’s bus routes.

As part of the test, various manufacturers will provide 40- and 60-foot battery powered buses for the performance test. The county will be testing buses before selecting a manufacturer to contract with. The test is part of Metro’s plan to deploy new zero-emissions busses in South King county as well as operating a no-emissions fleet by 2040. Part of this includes purchasing and using green buses as well as installing a high-powered charging station at a base facility. One station is based on the Eastside in Bellevue.

The announcement also follows a report on the environmental benefits of electric buses, which was released this summer by the Environment Washington Research and Policy Center. The release said buses cost less to maintain and can travel four times the distance per gallon than diesel-fueled buses.

This means that a full transition to electric buses in Washington state could avoid nearly 90,000 tons of pollution each year, equivalent to taking more than 17,000 cars off the road. The county plans on purchasing 120 all-electric buses by 2020 in an effort to meet its 2040 goals. The county’s fleet includes roughly 1,400 buses, many of which are hybrids that rely on diesel and electricity.

In previous coverage, the Seattle Weekly found that due to declines in electric vehicle battery costs and improvements in quality, governments using electric buses saved around $30,000 per bus each year compared to diesel-powered buses.

The report also said that exhaust from diesel-powered buses can cause breathing problems and worsen diseases like asthma. Diesel buses can include benzene and formaldehyde.

Additionally, a 2017 report found that King County Metro buses consumed around 10 million gallons of diesel annually and accounted for 80 percent of emissions from the county government.