The California Air Resources Board (ARB) staff conducted a second field study in 2011/2012 similar to the first study but with new heavy‑duty diesel (HDD) engines tested. The investigations included (1) a follow-up survey of diesel exhaust fluid (DEF) availability with the State of California, (2) roadside inspections to determine whether truck operators driving Selective Catalyst Reduction (SCR) equipped trucks on California roadways have tampered with SCR components or are not using DEF, (3) a re-evaluation of driver inducements on two SCR-equipped 2010 model year (MY) Cummins engines evaluated in the first study where error in programming and part malfunctions were found, (4) a continued evaluation of 2010+ MY NOx control strategies including an examination of the types and effectiveness of SCR driver inducements employed on SCR-equipped trucks, and (5) an examination of the emission impacts of HDD vehicles.
