Using the worldwide-traveling Hokule‘a docked at Pokai Bay as inspiration, leaders from all four major counties Tuesday signed pledges to eliminate the use of fossil-fuel-powered ground transportation vehicles by 2045.

The joint proclamation signed by Honolulu Mayor Kirk Caldwell, Maui Mayor Alan Arakawa, Kauai Mayor Bernard Carvalho Jr. and Hawaii County Managing Director Wil Okabe sets 2045 as the target date for both public and private ground transportation vehicles in the state to be fueled by renewable energy.

Caldwell, Arakawa and Carvalho additionally committed to using only renewable energy to power their government vehicles 10 years earlier — by 2035.

The proclamation does not apply to air or sea transportation.

Josh Stanbro, Honolulu’s chief resilience officer, said long-term planning will be needed to determine how the goal will be achieved. “But the idea is that it’s agnostic in terms of what type of clean energy it is — it could be hydrogen, it could be electricity, it could be renewable biofuels. So long as it it’s not fossil-fuel-based fuel.”

Steering away from fossil-fuel-powered vehicles is not just the right thing to do from an environmental standpoint, it saves the government money, Stanbro said. The electric vehicles that the city uses today cost a third less in operations and maintenance costs than do fossil-fueled counterparts, he said.

Motor vehicle manufacturers already have begun to go electric only, Stanbro said. Swedish automaker Volvo pledged this past summer to build only electric or hybrid vehicles starting in 2019. Tesla started as an electric-vehicle-only manufacturer in 2003.

Ground transportation accounts for more than 25 percent of the state’s consumption of imported fossil fuels.

To help lay the groundwork for the 2045 goal, the mayors will work with private partners to develop the infrastructure necessary to accommodate new types of fuel including electricity, hydrogen and renewable diesel.

Several of the speakers at Tuesday’s news conference cited Hokule‘a’s Malama Honua Worldwide Voyage and its message for people across the globe — to take care of the planet and make it sustainable — as a shining model for them.

“Human activity created climate change, and human action’s going to reverse it,” Caldwell said. Besides powering the upcoming rail line with electricity, the city will begin converting its 500-plus bus fleet to all-electric beginning in January, he said. “That fleet should be converted over by 2035.”

The next step will be to convince private companies to steer their fleets away from fossil-fueled vehicles, he said.

“We can’t change the direction of the wind, but we can adjust our sails to reach our destination,” Carvalho said.

Nainoa Thompson, Hokule‘a master navigator, called Tuesday’s news conference a historic moment. “It’s a moment of history, it’s a moment of vision, it’s a moment of making promises, it’s a moment of courage and it’s a moment of unity,” he said.

Thompson retold the story of how the leaders of the Polynesian Voyaging Society and Hokule‘a made the final decision to embark on the worldwide journey. Ultimately, he said, the increasing news about sea level rise, climate change and other environmental issues led the leaders to determine that the risk of inaction was more dangerous than the risks of the journey itself, he said.

“What’s more dangerous?” Thompson asked. “The pirate? The hurricane? The rogue wave? Or being tied to the dock and being too afraid to go?”