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A coalition of scientists and health experts is calling on the California Air Resources Board (CARB) to implement a more stringent Advanced Clean Trucks (ACT) rule. The authors argue that heavy-duty vehicles are disproportionately polluting, contributing significantly to global warming and public health crises, particularly in communities of color. They specifically criticize CARB's current proposal, which would result in zero-emissions vehicles making up only 4 percent of trucks on California roads by 2030, and advocate for higher sales standards to accelerate the transition from diesel to zero-emissions technologies.

The document examines the production and use of renewable natural gas (RNG) as a climate strategy in the United States, focusing on its potential to reduce greenhouse gas (GHG) emissions when derived from organic waste. It identifies that RNG is most effective when produced from waste rather than dedicated land and when it results in net methane emissions reductions. The paper highlights promising feedstocks such as food and yard waste diverted from landfills and livestock manure. While RNG production costs are higher than conventional natural gas, the report notes that economic viability is supported by low-carbon fuel standards and federal incentives. However, it warns that RNG can increase net methane emissions if it comprises 'new methane'—methane that would not have otherwise entered the atmosphere—due to supply chain leakage. The authors call for more data on methane leakage and life-cycle carbon intensities to better integrate RNG into long-term climate plans.

The study finds that a significant portion of diesel vehicle emissions in 11 major markets exceed certification limits, contributing to 38,000 premature deaths globally in 2015. Heavy-duty vehicles are the primary source of these excess emissions. Implementing next-generation standards beyond Euro 6/VI could avoid approximately 174,000 premature deaths by 2040.

The document examines biomethane derived from landfills, wastewater treatment centers, and dairies as a replacement for diesel and natural gas in California's heavy-duty vehicle fleets. While acknowledging its climate benefits over fossil fuels, the authors highlight that California's total biomethane potential from waste would meet only 3% of the state's natural gas demand and 15% of its diesel consumption. The report warns that promoting compressed natural gas (CNG) vehicles could inadvertently increase reliance on fossil natural gas due to this supply gap. It concludes that biomethane provides the greatest emissions reductions when used to generate electricity or hydrogen for electric vehicles, but that battery electric vehicles powered by the grid remain the most effective path for meeting climate goals.

The document argues that electrifying heavy-duty vehicles in California can significantly reduce air pollution and global warming emissions while creating job opportunities for underserved communities. It provides a life cycle emissions analysis comparing battery and fuel cell electric buses to diesel and CNG alternatives, finds that current EV technology meets many urban operational needs, and recommends targeted workforce training and financial incentives to ensure an equitable transition.

The document provides a technical appendix describing the life cycle emissions modeling for urban buses in California, comparing diesel, compressed natural gas (CNG), hydrogen fuel cell, and battery electric options. It details modifications to the CA-GREET 2.0 and Vision 2.0 models to better reflect California-specific fuel pathways and electricity grid mixes. Key findings include the significant reduction of global warming emissions when using 100% renewable energy for electric buses and the role of biomass and coal in the grid's particulate matter emissions. The analysis also examines the impact of low-carbon biofuels and low-NOx engines on overall emissions profiles.

The document analyzes proposed US heavy-duty vehicle standards for model years 2018–2029, noting they would reduce oil consumption by 550,000 barrels per day by 2035 and avoid 1 billion metric tons of emissions. However, the Union of Concerned Scientists (UCS) argues that a 40 percent reduction in fuel consumption is achievable by 2025, which would save an additional 200,000 barrels of oil per day and avoid 40 million metric tons of annual emissions compared to the government's 36 percent target for 2027.

The report argues that independent owner-operators in the U.S. are trapped in a cycle of using inefficient used Class-8 trucks due to subprime credit status and high upfront costs for new vehicles. It proposes the Federal Freight Efficiency Authority (FFEA), modeled after the Federal Housing Administration (FHA), to insure lease payments for new, efficient trucks. This mechanism would lower interest rates for truckers, increase their profit margins, and incentivize OEMs to produce more efficient vehicles. The author estimates that expanding this to small fleets could reduce Class-8 fuel consumption by 32%, saving 55 billion gallons of oil over ten years. The FFEA would be self-funded through insurance premiums and could potentially supplement the Highway Trust Fund with its profits.

The document identifies black carbon from diesel engines as a potent warming pollutant and proposes the widespread adoption of diesel particulate filters (DPFs) to achieve immediate climate and public health benefits in the United States.

The analysis finds that retrofitting U.S. Class 8 trucks with DPFs provides significant near-term climate benefits by reducing black carbon, a potent warming agent. Using a 'best estimate' 20-year global warming potential (GWP20) of 2,200, the study calculates a net benefit of approximately 2,080 gCO2e per gallon of diesel fuel, even when assuming a conservative 2% fuel penalty. The report concludes that such retrofits are climate-beneficial as long as the fuel penalty remains below 22% (GWP20) or 7% (GWP100). A hypothetical rebuild rule retrofitting nearly one million trucks between 2012 and 2030 would result in a total CO2e reduction of 96 million metric tons (GWP20), equivalent to eliminating the annual emissions of 21 million cars.

The report assesses the potential for reducing greenhouse gas (GHG) emissions, NOx, and fuel consumption in California's heavy-duty truck fleet through retrofit technologies. It evaluates six technology packages across different vehicle types and duty cycles, concluding that a combination of high-technology retrofits for new vehicles and moderate-technology retrofits for in-use vehicles is the most cost-effective strategy. The analysis suggests that focusing on tractor-trailers and straight trucks over 14,000 pounds could reduce state heavy-duty fleet GHG emissions by 14.9 to 22.2 million metric tons of CO2-equivalent between 2010 and 2020.

The fact sheet outlines how a California green bank could accelerate decarbonization in the transportation sector, which contributes roughly 40 percent of the state's GHG emissions. It proposes interventions across four areas: passenger vehicles, zero-emission vehicle (ZEV) infrastructure, goods movement, and regional planning. Key proposed mechanisms include providing credit enhancements to expand private lending for low-carbon vehicles and heavy-duty trucks, coordinating risk and financing for EV infrastructure to overcome the 'chicken-and-egg' challenge of adoption versus availability, supporting at-scale innovative freight infrastructure, and financing projects to reduce vehicle miles traveled (VMT).

The report argues that retrofittable efficiency technologies can offset fuel economy losses caused by 2002 and 2007 emissions regulations. It proposes two implementation scenarios for Canada's 294,000 Class-8 trucks: a 'full package' of all efficiency devices and a 'simple package' adopted by 50% of the fleet. The report emphasizes that government leadership, technical guidance, and financial incentives are essential to overcome industry obstacles and accelerate the adoption of these technologies.

The document outlines a technical framework for calculating fuel use across various truck types—including tractor-trailers, straight trucks, and cargo vans—using data from the Freight Analysis Framework (FAF) and the Vehicle Inventory and Use Survey (VIUS). It establishes baseline fuel economies (e.g., 5.8 mpg for tractor-trailers) and projects improvements by 2025 based on technology packages such as aerodynamic devices and hybrid-electric powertrains. Additionally, it applies these methodologies to estimate the current fuel use and future savings for the fleets of UPS, FedEx, PepsiCo, The Coca-Cola Company, and Walmart.

The analysis finds that seven global transport initiatives could reduce global energy-related emissions by 3.7 percent by 2050. The most significant reductions are linked to mode-shifting to rail or public transport, though these require high effort. While electric vehicle and fuel efficiency targets are ambitious, the paper notes gaps in addressing heavy-duty vehicles and total travel demand, suggesting that better policy linkages and wider geographical coverage are needed to improve effectiveness.