California Air Resources Board

SACRAMENTO – The California Air Resources Board (ARB) today adopted a regulation that will further reduce air pollution from the state's transit buses, and require some fleet operators to start using zero-emission buses (ZEBs) in three years.

       "This regulation cuts air pollution right where it is most troublesome -- in the heart of our cities where 90 percent of Californians live," said ARB Chairman Dr. Alan Lloyd.

       The regulation, which in 2002 starts its phase-in, affects about 8,500 buses at approximately 75 California transit agencies.

       It moves forward in several steps over the next ten years, requiring cleaner engines, cleaner diesel fuel, retrofit to reduce exhaust particulate matter (PM) emissions from older diesel buses, use of ZEBs and reduced exhaust PM and nitrogen oxides (NOx) from new diesel engines. Diesel exhaust PM contributes to mortality and contains substances known to cause cancer,  while NOx contributes to ozone, the main harmful component of urban smog.

       The regulation allows transit agencies the flexibility of choosing between either a diesel or alternative fuel "path" to lower air emissions. Agencies may choose to use low-emission alternative fuels such as compressed or liquefied natural gas, propane, methanol, electricity, fuel cells or other advanced technology.  Continued use of diesel brings with it a requirement to use low-sulfur (15 parts-per-million) diesel fuel beginning July 1, 2002, and cut emissions from new diesel buses by another 75 percent beginning in 2004.  An even lower NOx standard applies to both diesel and alternative fuel bus engines sold to California transit agencies starting in 2007.

       In addition, for both diesel and alternative fuel paths, a NOx fleet average of 4.8 begins in 2002, which will require some transit agencies to retire their oldest, highest polluting buses.  A requirement to retrofit existing buses with traps or other devices to reduce PM starts in 2003.  When the requirements are fully implemented, all transit buses will be smoke-free and will emit less smog forming emissions.

       "The regulation is designed to bring quick, near-term emissions reductions and long-term, near-zero emission benefits," Dr. Lloyd said.

       Large transit agencies with 200 or more buses that continue to purchase primarily diesel vehicles are required to begin demonstrating the use of at least three ZEBs by 2003. ZEBs powered by electricity or hydrogen fuel cells are already being used by some transit agencies.

       From model year 2008 through 2015, large transit agencies using diesel will be required to make ZEBs 15 percent of their new bus purchases/leases.  For large transit agencies using primarily alternative fuels, the 15 percent ZEB rule runs from model year 2010 through 2015.

       And, since federal, state and local governments heavily subsidize bus costs, it is possible to invest in purchases of new, cleaner buses without adversely affecting transit service.

       ARB staff calculates that the new transit bus rules, combined with normal fleet turnover, will bring statewide reductions of seven-tons-per-day of NOx and 12 tons-per-year of PM by 2020.

We have made available the "Urban Transit Bus Fleet Rule Requirements and Emission Standards" below in Word97 and PDF.