Ultra-Low Nox Natural Gas Vehicle Evaluation by UC Riverside

A report released by the University of California Riverside’s College of Engineering-Center for Environmental Research and Technology (CE-CERT), found that new ultra-low NOx natural gas heavy-duty vehicles met and were cleaner than their
certification standards during a full range of duty cycles. This finding is in stark contrast to previously released CE-CERT data of
heavy-duty diesel trucks that emitted higher levels of NOx than their certification standards in the same duty cycles. With the
near-zero emission factors demonstrated for natural gas vehicles, it is expected that these vehicles could play an important
role in providing much needed emissions reductions required for the South Coast Air Basin and California to reach federal
air quality attainment standards.

Here is the report itself.