June 20 (Reuters) - Hawaii on Thursday agreed to take action to decarbonize its transportation system by 2045 to settle a lawsuit by 13 young people alleging the U.S. state was violating their rights under its constitution with infrastructure that contributes to greenhouse gas emissions and climate change.

Democratic Governor Josh Green announced the "groundbreaking" settlement at a news conference attended by some of the activists and lawyers involved in the lawsuit, which they called the first-ever youth-led climate case seeking zero emissions in transportation.

They argued that the state had prioritized infrastructure projects such as highway construction and expansion that lock in the use of fossil fuels rather than focusing on projects that cut carbon emissions.

"We're addressing the impacts of climate change today, and needless to say, this is a priority because we know now that climate change is here," Green said. "It is not something that we're considering in an abstract way in the future."

The case had been set for trial on Monday. It would have been the second-ever trial in the United States of a lawsuit by young people who claim their futures and health are jeopardized by climate change and that a state's actions violated their rights.

As part of the settlement, Hawaii will develop a roadmap to achieve zero emissions for its ground, sea, and inner island air transportation systems by 2045, the year by which the state was already aiming to become carbon neutral.

The agreement, which can be enforced in court, calls for the creation of a volunteer youth council to advise the state's Department of Transportation, which committed to reworking its planning to prioritize reducing greenhouse gasses and creating a new unit dedicated to decarbonization.

The department also plans to dedicate at least $40 million to expanding the public electric vehicle charging network by 2030 and accelerate improvements to the state's pedestrian, bicycle and public transit networks.

Leinā'ala Ley, a lawyer for the youth activists at Earthjustice, said the "agreement gives Hawaii a boost in our race against climate disaster and offers a model of best practices that other jurisdictions can also implement."

The case is one of several by young environmental activists in the United States that broadly accuse governments of exacerbating climate change through policies that encourage or allow the extraction and burning of fossil fuels.

The young people, also represented by the nonprofit law firm Our Children's Trust, claim the policies violate their rights under U.S. or state constitutions.

The cases have raised novel legal claims and have been dismissed by several courts. But the young activists scored a major victory last year when the first such case went to trial in Montana.

In that case, a Montana judge concluded that the Republican-led state's policies prohibiting regulators from considering the impacts on climate change when approving fossil fuel projects violate the rights of young people.

The lawsuit against Hawaii was filed in 2022 and alleged the state Department of Transportation was operating a transportation system that ran afoul of state constitutional mandates and impaired their right to a life-sustaining climate.

The plaintiffs, ages 9 to 18 when the case was filed, argued that the state was violating a right guaranteed by the Hawaii Constitution to a clean and healthful environment and its constitutional duty to "conserve and protect Hawaii's natural beauty and all natural resources."

The state spent $3 million fighting the case and seeking its dismissal, arguing the zero emissions target and other state laws adopted by the state legislature promoting reduced carbon emissions were "aspirational" and could not form the basis of claiming the state was violating the young people's rights.

But Judge Jeffrey Crabtree in Honolulu rejected that argument in April 2023, saying the laws required timely planning and action to address climate change and that the state's inactions had already harmed the plaintiffs.

"Transportation emissions are increasing and will increase at the rate we are going," Crabtree said. "In other words, the alleged harms are not hypothetical or only in the future. They are current, ongoing, and getting worse."