The NCDOT Rail Division implemented a Selective Catalytic Reduction (SCR) after-treatment system onto one (1) of its locomotives as a means of reducing engine emissions to at or near the EPA Tier 4 standard.

The NCDOT Rail Division replaced the CAT 3412C Head End Power (HEP) engines in two of its passenger locomotives with new CAT C15 engines.  The CAT 3412 is a mechanically injected, 1980s technology engine which was built before the issuance of EPA diesel emissions standards; thus it is non-compliant with current EPA standards.