Zero-Emission School Bus Adoption in California

• Health Benefits
• Emissions Reductions
• Cost Savings
• California School Bus Regulations

School buses powered by fossil fuels emit harmful exhaust that can pose serious health risks to children. These risks include asthma, bronchitis, impaired lung development, cancer, and other respiratory illnesses.  

Although children spend less than 10% of their day commuting to school, a 2003 study by the California Air Resources Board (CARB) found that riding in a diesel-powered school bus can account for up to 33% of a child’s daily exposure to certain air pollutants.  

ZE school buses eliminate tailpipe emissions, providing cleaner air for students and communities — especially in overburdened neighborhoods. Additional benefits include:

• Holistic student health and classroom readiness: Since ZE school buses don’t have an internal combustion engine (ICE), the buses provide a quieter, more relaxing ride to prepare children for learning. 

• Reduced noise pollution: ICE school buses produce noise levels at or above 85 decibels, exceeding the Environmental Protection Agency’s recommended noise exposure limit of 80 decibels for children. ZE school buses, which average 20 decibels quieter than diesel buses, are especially beneficial for children with sensory sensitivities who require a quiet environment for regulatory needs.
• Improved attendance rates: Asthma attacks are a leading cause of health-related absenteeism, according to the Centers for Disease Control and Prevention. By removing harmful emissions from student transportation, ZE school buses can provide a safe, reliable, and consistent way to get to school while reducing health risks.

State and federal emission standards have played an important role in reducing children’s exposure to harmful pollutants. In California, ongoing efforts to combat climate change have led to regulations that will reduce greenhouse gas emissions while improving air quality and protecting public health. 

While alternative fuels can provide some reduction in emissions over conventional diesel, in many cases, the tradeoff for reducing one emission is at the cost of increasing another. According to the World Resources Institute, compared to conventional diesel: 

• Propane and E85 produce lower emissions of nitrogen oxides and sulfur oxides, but higher emissions of volatile organic compounds (VOCs), carbon monoxide, and similar levels of particulate matter (PM).

• Compressed natural gas (CNG) and liquefied natural gas (LNG) buses, which are no longer on the school bus market, produce lower emissions of nitrogen oxides and sulfur oxides, but higher carbon monoxide emissions and similar levels of VOCs and PM.
• Biodiesel and renewable diesel produce lower emissions of sulfur oxides, but other tailpipe emissions remain the same.  

ZE school buses have no tailpipe emissions, so students, drivers, and communities are protected from dangerous air pollutants such as PM and oxides of nitrogen. Even when accounting for emissions associated with electricity production, ZE school buses produce fewer total greenhouse gas emissions than fossil fuel-powered models, particularly as California is now projected to generate over 50% of electricity from renewable energy. 

California is committed to meeting both state and national air quality standards, achieving climate and clean air goals, and protecting public health through incentive programs, vehicle standards, outreach and education, and complementary programs and policies that enable ZE vehicle deployment. An example of this commitment is California’s Zero-Emission School Bus and Infrastructure Project. Through this project, CARB estimates that replacing an old school bus with a ZE equivalent will yield annual per-vehicle emissions reductions of 18 metric tons of carbon dioxide equivalent, 0.122 tons of nitrogen oxides, 0.000677 tons of fine particulate matter, and 0.00128 tons of reactive organic gases.

Over time, districts can see cost reductions through less expensive fuel use and decreased maintenance needs. Additional benefits, such as potential revenue opportunities from programs like California’s Low Carbon Fuel Standard (LCFS) can also help ease the financial burden over the life of the vehicle. 

These advantages are reflected in the performance and cost characteristics of ZE school buses. According to the World Resources Institute, ZE school buses generally have lower operational costs compared to diesel models. Research shows that districts can save on average $7,000 per year for every new ZE school bus. 

Maintenance costs for a new Type C ZE school bus average $0.35 per mile, while a comparable diesel school bus averages $0.69 per mile. Districts that made the switch report spending one-third of the fuel cost on their new ZE buses and increased fuel efficiency, comparatively. Despite initial higher purchase prices, these operational savings can improve affordability over time.

Starting in 2035, California legislation, Assembly Bill 579 (Ting, 2023), will require that 100% of newly purchased or contracted school buses be zero-emission. This legislation allows local educational agencies to request one extension not to exceed five years if purchasing zero-emission vehicles is not feasible due to both terrain and route constraints (certain conditions must be met). Frontier local agencies will be eligible to apply for additional extensions annually through January 1, 2045.   

The legislation is part of the state’s larger effort to become carbon neutral by 2045, and recognizes that advances in the transportation sector are essential to meet the broader target.