The California Air Resources Board (ARB) staff conducted field investigations into the implementation of 2010 model year (MY) on-road heavy‑duty diesel (HDD) engines equipped with Selective Catalytic Reduction (SCR). The investigations included: (1) two surveys of diesel exhaust fluid (DEF) availability within the State of California, (2) a survey to determine whether truck operators driving 2010 MY SCR-equipped trucks on California roadways have tampered with SCR components or are not using DEF, (3) an examination of the types and effectiveness of SCR driver inducements employed on 2010 MY HDD vehicles, and (4) an examination of the emission impacts of HDD SCR-equipped vehicles when DEF has been depleted, diluted or the SCR system has been tampered with.
