Union of Concerned Scientists

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Clean Buses for California

A new diesel transit bus emits 40 times more pollution over its life than the average car. California regulators responded by voting on February 24, 2000, to reduce smog-forming exhaust from a new diesel bus by an additional 90 percent and cut harmful toxic soot particles by 80 percent starting in 2007. Not only will these new standards help clean up the air in California's crowded urban centers, they will also serve as a template for new standards on diesel trucks nationwide.

The new standards include the following requirements:

• New buses must emit 90 percent less smog-forming exhaust and 80 percent fewer soot particles by 2007.
  
  
• 15 percent of the buses purchased by the state's largest transit agencies must be zero emission buses (for example, powered by hydrogen fuel cells) starting in 2008.
  
• Transit agencies must retrofit or replace dirtier diesel buses already in their fleets.
  
  
• Transit agencies are encouraged to buy cleaner, alternative-fuel buses today because by doing so they will face less stringent regulations over the next few years.
  
  

UCS helped lead the coalition of California environmental and public health groups in advocating for stiffer rules. We authored the coalition's technical comments on the draft rule, led meetings with the state's top regulators, industry representatives, and transit agencies, and worked with media to draw attention to this landmark decision.

Although the final rule preserves diesel's role in California transit buses, UCS will continue to advocate at the local level for cleaner, alternative-fuel buses. In finalizing the new state rule, regulators clearly stated that alternative-fuel buses are cleaner than even the newest diesel buses required. In fact, UCS estimates that local transit agencies that purchase alternative fuel buses will spare their populations from 2 to 5 times less toxic soot than if they continue buying diesel buses.

These tighter standards won in California became the starting point for the new federal regulations on all diesel trucks that passed in January 2001. This small step for cleaner buses in California could yielded a huge leap for reducing diesel pollution nationwide.