Project at a Glance

Title: Measuring real-world emissions from the on-road heavy-duty truck fleet

Principal Investigator / Author(s): Kirchstetter, Thomas

Contractor: UC Berkeley

Contract Number: 12-315

Research Program Area: Emissions Monitoring & Control

Topic Areas: Field Studies, Mobile Sources & Fuels, Modeling, Transport


California Air Resources Board (CARB) regulatory programs have targeted emission
reductions of particulate matter (PM) and oxides of nitrogen (NOX) from heavy-duty
vehicles (HDVs) over the past decade, and real-world emissions measurements of
the current fleet are essential for evaluating the efficacy of the programs. Emissions
of PM, NOX, particles, and gas-phase nitrogen species from HDVs at the Caldecott
Tunnel (Oakland, CA) were quantified in 2014, 2015, and 2018 via a plume capture
sampling method and matched to license plates. As diesel particulate filter (DPF)
penetration increased to 91 percent and selective catalytic reduction (SCR) to
59 percent, black carbon (BC) emissions decreased by 79 percent and NOX
emissions decreased by 57 percent. Issues with DPFs were identified in a small
number of "high-emitters," with 3.8 and 3.2 percent of the fleet emitting half of
fleet-averaged BC in 2014 and 2018, respectively (a relative decrease of 16 percent).
NOX emissions were less skewed, with the fleet portion contributing half of all NOX
decreasing from 20.1 to 14.2 percent over that same time period. Fleet-averaged BC
emissions decreased from 0.41 to 0.18 g/kg fuel over these four years, while NOX
decreased from 16.3 to 13.2 g/kg fuel. NOX emissions from SCR-equipped vehicles
at this site were still broadly higher than predicted based on certification standards.

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

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