Date of Award


Document Type


Degree Name


Organizational Unit

Chemistry and Biochemistry

First Advisor

Brian Majestic, Ph.D.

Second Advisor

Mark Siemens, Ph.D.

Third Advisor

Bryan Cowen

Fourth Advisor

Alex Huffman

Fifth Advisor

Erich Chapman


Fuel emissions, On-road heavy-duty, Vehicle emissions measurement system, Fuel efficiency automobile test


New heavy-duty vehicle regulations have caused significant reductions in hazardous air pollutants, such as particulate matter (PM) and nitrogen oxides (NOx), due to better engine management and utilization of advanced after-treatment systems. The University of Denver has collected data for gaseous and PM emission measurements from on-road heavy-duty vehicles (HDVs). The On-Road Heavy-Duty Vehicle Emissions Measurement System (OHMS) collected fuel specific emission information on individual HDVs of in-use fleets at two California locations in the spring of 2013, 2015 and 2017. These complimentary fleets, studied over multiple years, produced 7,075 measurements of gaseous and particle emission data providing the basis to quantify on-road HDV emission trends and compare a variety of factors that influence on-road emissions. The Port of Los Angeles contributes a fleet fully equipped with diesel particulate filters (DPFs) that had an observed PM increase of 30% in 2017 from 2013, but the fleet average is highly dependent on the fraction of high emitters. The second fleet measured was at the Cottonwood weigh station in Northern California, regulated at the state level and with slower fleet turn over, fleet PM emissions decrease (76% between 2013 and 2017) but at a slower rate than at the Port.

Additionally, heavy and medium-duty vehicles were measured at a second weigh station in Southern California. The Fuel Efficiency Automobile Test (FEAT) was used to collect on-road fuel specific emissions for HDVs and MDVs at the Peralta weigh station near Anaheim, CA, resulting in 2,315 measurements. The HDV’s data added to measurements from 1997, 2008, 2009, 2010 and 2012 at this location. Two FEAT systems, one traditionally mounted atop scaffolding to collect emissions from HDVs with elevated exhaust stacks and a second, ground-level system were used for the first time to measure emissions from both MDVs and HDVs with ground-level exhaust. Introduction of new technologies show diminished NOx and PM emissions as HDVs saw a 55% NOx decrease since 2008 and a 33% reduction in IR %opacity. The MDV fleet was 2.1 years older than the HDV fleet and MDVs NOx emissions show reductions approximately 2 model years (2014) earlier than HDVs.

Publication Statement

Copyright is held by the author. User is responsible for all copyright compliance.

Rights Holder

Molly J. Haugen


Received from ProQuest

File Format




File Size

163 p.



Included in

Chemistry Commons