Study: California must totally retire heavy-duty trucks to meet 2045 carbon goals

California must retire existing heavy-duty trucks and promote the purchase of zero-emission vehicles (ZEVs) to meet its 2045 carbon neutrality goals, according to a new study published Monday.

Stricter policies covering both the early retirement of gas-intensive vehicles and the rollout of ZEV trucks could reduce greenhouse gas emissions by 64%, according to the study published in Environmental Research: Infrastructure and Sustainability. 

As the world’s fifth-largest economy, California generates roughly 0.75% of global greenhouse gas emissions. Heavy-duty vehicles alone contribute about 8% of the state’s total emissions, generating some 32 million tonnes of carbon annually. 

While trucks represent just 6% of the vehicles on California roads, they account for over 35% of the state’s transportation-generated nitrogen oxide emissions and 25% of the state’s on-road greenhouse gas emissions, according to state data.

“While ZEV sales mandates are effective, it is clear from our analysis that they will not be sufficient for reaching zero emissions on the desired timescales,” lead author Eleanor Hennessy, a postdoctoral scholar at Arizona State University, said.

“Accelerated retirement programs will be critical for California to reach emissions targets by 2045,” Hennessy added. 

The study said that instituting decarbonization policies that combine both ZEV adoption and long-haul, as well as heavy-duty combustion engine truck retirement, would yield widespread benefits and enable the state to meet its long-term climate targets. 

The move would also reduce half of California’s pollution-related mortality, particularly within disadvantaged communities – which often bear the brunt of climate impacts – the authors determined. 

Cost of converting

The authors acknowledged that removing gas-powered heavy-duty vehicles “comes at a cost,” as the owners would likely require compensation from the state to prevent resales outside of California. They recommended that state officials prioritize eliminating vehicles whose removal would be most cost-effective. 

“Early retirement of long-haul heavy heavy-duty trucks, and heavy heavy-duty trucks operating in ports would have the greatest net benefit, along with the largest magnitude of reduced climate and health damages,” they concluded.

California has distributed more than US$780 million to help fleet operators purchase ZEV trucks, the state said. Some US$10 billion of its US$52 billion climate commitment will be allotted to accelerate the ZEV transition and build charging infrastructure. 

State of ZEVs in the state

California announced in late 2023 that it had exceeded both its passenger and truck ZEV sales goals two years ahead of schedule, with 7.5% of all new trucks sold in 2022 being ZEVs. The goal was to hit 6% by 2024. 

California also surpassed its passenger vehicle ZEV goal by more than 1.5 million ZEV sales two years before its 2025 goal, the governor’s office said. 

The state currently aims to have half of all new medium- and heavy-duty truck sales ZEV by 2035, with an ultimate goal of 100% ZEV trucks sold by 2045. The state’s Advanced Clean Trucks rule requires that an increasing share of new trucks sold in California be ZEV from 2024. Similarly, the Advanced Clean Fleets rule requires that medium- and heavy-duty fleets start a phased-in transition toward ZEVs from 2024. 

The transition has not gone without pushback. In two separate lawsuits, a coalition of 24 states filed a petition for review in May to challenge the Biden Administration’s greenlighting of California’s EV policy. A separate coalition of 17 states filed a lawsuit in California seeking to block the state’s Advanced Clean Fleets rule.