California Air Resources Board

School bus vehicles powered by diesel fuel with a gross vehicle weight rating (GVWR) of greater than 14,000 pounds that provide transportation of any school pupil at or below the 12th-grade level or to or from a public or private school, or to or from public or private school activities are subject to the Truck and Bus Regulation.

Previously, school buses that could not be retrofitted (e.g. 2-stroke engine buses), could delay their compliance until January 1, 2018 with an approved extension.

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