Clean School Buses

Mobile source emissions are major contributors to the potential cancer risk from air pollution. Long-term epidemiological studies of school age children conducted by University of Southern California and University of California, Los Angeles indicate that nitrogen oxides and particulate matter have much greater impacts on limiting lung growth in children than believed in the past. These include exhaust emissions from high emitting diesel-fueled school buses that contain smog forming pollutants and air toxics harmful to school children. As a result, SCAQMD adopted Rule 1195 (PDF, 29kb) – Clean On-Road School Buses. This Rule requires public schools and private operators with more than 15 or more school buses to purchase or lease cleaner school buses that better protect school age children.

Old School Buses Replaced

SCAQMD has also adopted the Lower-Emission School Bus Incentive Program. There are thousands of older school buses on the road that have remained in service primarily because school districts lack funds to replace them. Using state, federal and its own matching funds, SCAQMD has provided substantial incentives to public school districts to purchase new very clean natural gas buses and low-emitting diesel buses. In turn, these districts have to retire an equivalent number of the oldest, highest-polluting buses in their fleets: first, pre-1987 buses and then pre-1994 buses. Program Flyer. (PDF, 691 KB)

PM Traps

SCAQMD has provided further incentives to both school districts and private operators to install particulate trap filters that eliminate 85 percent or more of particulates in diesel exhaust. School buses eligible for particulate traps are 1994 and newer diesel buses that must use low-sulfur diesel fuel, with 15 ppm or lower sulfur content. SCAQMD has awarded PM traps to retrofit nearly 3,400 diesel buses.

CNG Tank Replacement

CNG tanks have a typical 15 year life. Commencing Calendar Year 2012 the SCAQMD launched an incentive program providing funding to public school districts to replace expiring CNG school bus tanks 14-16 years old. SCAQMD provides $20,000 per CNG bus to replace the expired CNG tanks with new CNG tanks. The new tanks have at least a 20 year life and will last for the remainder of the school bus life.

A related program also offered by the SCAQMD provides funding for particulate trap filters or stationary backup diesel generators located at or within 500 feet of a school site.  

There are a number of environmental justice considerations that must be met by any clean school bus project proposed for funding under this incentive program. These funding criteria ensure that funds reach communities disproportionately impacted by poor air quality, communities with higher poverty levels, and communities with higher risk of particulate matter and toxic exposure.

$300 million awarded for school bus replacement and retrofits

As of 2016, SCAQMD has awarded nearly $300 million to replace nearly 1,600 pre-1994 school buses with clean alternative school buses having the latest safety features. 90 percent of these new school buses have been the large size CNG Type D buses, and the remainder 10 percent were propane powered Type C buses. These awards also included PM traps, to retrofit nearly 3,400 diesel buses, PM traps that reduce toxic fine particulate exhaust by over 85 percent. 

Overall, as a result of these awards, about 4,900 school buses are currently operating that meet stringent air quality standards. At about 60 to 70 kids being transported per bus, this translates to nearly 300,000 kids traveling daily in some of the cleanest school buses in the country, the vast majority of them in Environmental Justice areas. The SCAQMD program is, thus, the largest of its kind in the country.

Any available funding opportunities for clean school buses can be found on SCAQMD’s Grants & Bids page.

A pre1994 diesel bus

Filling a single bus

Diesel bus dismantled


For more information, contact:
Vasken Yardemian, Program Supervisor
Science and Technology Advancement

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