In this work, a novel remote sensing technology takes a snapshot of several pollutants’ emission rates for each passing truck, including nitrogen oxide, nitrogen dioxide, nitrous oxide, and black carbon. Researchers track the change in these emission rates over time at many locations to understand how emissions change with the introduction of new emission control technologies.

Emissions from thousands of in-use heavy-duty diesel trucks were sampled at a highway and an arterial street location in the San Francisco Bay Area, spanning a period when the use of diesel particle filters and selective catalytic reduction increased rapidly.

Selective catalytic reduction systems installed on 2010 and newer engines reduce emitted nitrogen oxides relative to pre-2004 engines but increase emissions of nitrous oxide and ammonia, respectively. Emissions of all nitrogenous species and especially NH₃ are skewed; 10% of trucks contribute 95% of the on-road fleet’s total NH₃ emissions. The emission changes due to the rapid adoption of diesel particulate filters and selective catalytic reduction systems by the California truck fleet result in an estimated 65% net decrease in the social cost of statewide exposure to diesel truck emissions and a 3% net decrease in the global warming potential-weighted emission factor.

See article "Update: Impacts of Heavy-Duty Diesel Truck Emissions" for more research efforts in this area.

Berkeley Lab analyzes data from vehicle emissions inspection and maintenance (I/M) programs managed in several states. The data include I/M test and on-board diagnostic scan results, remote sensing measurements, roadside pullover test results, and vehicle registration records. We have used the data to analyze various aspects of the effectiveness of inspection and maintenance programs in Arizona; California; Colorado; and Ontario, Canada; including estimated emission reductions, repeat failure rates, and aspects of motorist non-compliance with program requirements. The data also provide a rich resource to understand the distribution of in-use vehicle emissions by location and vehicle type and age.

The California Legislature created the Air District in 1955 as the first regional air pollution control agency in the country. The Air District is tasked with regulating stationary sources of air pollution in the nine counties that surround San Francisco Bay: Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, southwestern Solano, and southern Sonoma counties. It is governed by a 24-member Board of Directors composed of locally elected officials from each of the nine Bay Area counties, with the number of board members from each county being proportionate to its population.

The Board oversees policies and adopts regulations for the control of air pollution within the district. The Board also appoints the Air District’s Executive Officer/Air Pollution Control Officer, who implements these policies and gives direction to staff, as well as the District Counsel, who manages the legal affairs of the agency. The Air District consists of over 340 dedicated staff members, including engineers, inspectors, planners, scientists, and other professionals.

See more information about the district's work in measuring air quality at the Air District's website.

CARB is charged with protecting the public from the harmful effects of air pollution and developing programs and actions to fight climate change. From requirements for clean cars and fuels to adopting innovative solutions to reduce greenhouse gas emissions, California has pioneered a range of effective approaches that have set the standard for effective air and climate programs for the nation and the world.

Research sponsored by CARB

Strong science is at the foundation of California’s air quality and climate programs. The California Air Resources Board sponsors a comprehensive research program that investigates air pollution’s causes, effects, and solutions. The findings of this research support all the regulations on cars, trucks, fuels, power plants, and other pollution sources. The research, which results in five additional dollars for each dollar CARB invests, is done under the guidance of CARB’s Research Screening Committee and in partnership with the campuses of the University of California system and other research institutions.

CARB develops and conducts policy-relevant in-house and extramural research to advance the science and to support CARB mobile source programs and policies. Current research includes efforts to better understand the discrepancy between certification and real-world emission levels, achieve further emission reductions from on-road vehicles and off-road equipment, track and model the effect of various regulatory options to achieve real-world emission reduction targets using laboratory, portable emissions monitoring systems (PEMS), remote-sensing, and engine and activity data-logging technologies, and understand non-tailpipe emissions such as brake-wear, tire-wear, and resuspended roadside dust. CARB is also responsible for programs to reduce emissions of high global warming potential greenhouse gases from mobile air conditioners and to investigate the effect on emissions from advanced vehicle and low-carbon fuel technologies. Some activities include conducting large data-driven technical analyses, providing expert opinions to decision-makers, networking with internal, national, and international stakeholders, and publishing research findings.