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Project at a Glance

Title: Investigate the durability of diesel engine emission controls

Principal Investigator / Author(s): Stedman, Donald

Contractor: University of Denver

Contract Number: 11-309

Research Program Area: Emissions Monitoring & Control

Topic Areas: Mobile Sources & Fuels


The University of Denver has collected six data sets, each including approximately 1,200 fuel specific emission measurements, from two California fleets: a drayage fleet at the Port of Los Angeles and a long-haul interstate fleet at the Cottonwood weigh station. Collected between 2013 and 2017, they have been used to follow the introduction of diesel particulate filters (DPF) and selective catalytic reduction (SCR) after-treatment systems in heavy-duty trucks to control particulate and oxide of nitrogen (NOx) emissions. The Port fleet, a fully DPF equipped fleet by 2012, has steadily aged (+3.3 yrs. since 2103) and a small number of trucks were found with high particle emissions. NOx emissions have slowly increased (21 to 27 gNOx/kg of fuel) and lower operating temperatures are likely the reason that newer SCR equipped Port vehicles (2011 & newer) have not helped to lower these emissions. The Cottonwood fleet has experienced a steady fleet turnover and with the newer fleet (-1.7 yrs.) both particulate (0.22 to 0.08 gPM/kg of fuel) and NOx emissions (20.3 to 16 gNOx/kg of fuel) have declined. Newer SCR equipped vehicles at Cottonwood gives the promise of an additional factor of 3 reduction in fuel specific NOx emissions by 2023.


For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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