Regulation aims to clean up older California buses

Posted on June 8, 2010
Under the CARB’s Truck and Bus Regulation, older school buses — like this one operated by Kings Canyon USD — must be retrofitted with emissions-control technology.
Under the CARB’s Truck and Bus Regulation, older school buses — like this one operated by Kings Canyon USD — must be retrofitted with emissions-control technology.

SACRAMENTO, Calif. — The California Air Resources Board’s (CARB) Truck and Bus Regulation, drafted to reduce diesel-powered bus and truck emissions, will impact California school districts in the coming years.

By Jan. 1, 2014, all diesel-fueled school buses must be retrofitted with the highest level Verified Diesel Emission Control System (VDECS) available.

John Clements, director of transportation at Kings Canyon Unified School District (USD) in Reedley, Calif., has some concerns about meeting this requirement at his operation. Clements runs eight Crown Coach school buses equipped with large-block Cummins engines. Diesel particulate filter (DPF) manufacturers and installers have told him that if he retrofitted his Crown buses with DPFs, the buses would not make it through a day of service without plugging up with particulates.

“This is a serious safety concern for me as a director of transportation if students are stranded on a mountain or valley roadway,” Clements said.

As of press time, Clements had spoken with a CARB official who inform­ed him that because there is a CARB-verified DPF retrofit device available for his Crown buses, he must retrofit them by 2014; otherwise, he must replace them or take them out of service.

Clements also runs 11 school buses equipped with two-stroke Detroit Diesel engines, including nine manufactured between 1988 and 1993. He has retrofitted many of these buses with diesel oxidation catalysts to achieve a 25-percent reduction in particulate matter, but he said that there are no DPFs available to achieve the 85-percent reduction that the CARB desires.

A possible funding source to help air districts replace 1987 model year and newer buses may come from Assembly Bill (AB) 923.

The CARB determined that because no Level 3 retrofit devices have been CARB-verified for use on two-stroke engines, air districts may use AB 923 funds to replace buses powered by them.

“The key word is that the local air districts may fund replacements for buses with two-stroke engines,” Clements said. “The bottom line is, show transportation directors the funds and we will replace our school buses for the goals of improving air quality and student safety.”

Clements has also been in communication with Stephen Rhoads, a principal consultant for Strategic Education Services in Sacramento and a lobbyist for the School Transportation Coalition, to discuss other funding efforts for school bus replacements.

Clements said that Rhoads has told him that $11 or $12 billion will eventually be owed to the California education system through Proposition 98.

“We’ve discussed the possibility that a small sliver of that could be put toward a statewide bus replacement program based on chronological age,” Clements said.



Additional information

There are three main CARB school bus requirements. They can be found at (Click on the “Regulation” button and then scroll down to page 23 of the PDF.)
• For a list of CARB-verified retrofit devices, go to
• For more info, contact Heather Arias (, who oversees ARB’s school bus rules, or Lisa Jennings (, who can help school districts work with a fleet calculator to determine how many buses must be cleaned up by a specific year.

Related Topics: emissions, school bus replacement

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