Between 1999 and 2018, the California Air Resources Board (CARB), the California Inspection and Maintenance Review Committee and the Coordinating Research Council have sponsored studies to measure light-duty vehicles (LDV) exhaust emissions using a remote sensing device (RSD) at a West Los Angeles roadside location (ramp from South La Brea Avenue southbound to Interstate-10 eastbound). The longitudinal data shows that the LDV fleet has generally become cleaner over the years. Despite this progress, however, LDVs continue to be a major source of oxides of nitrogen (NOX) and reactive organic gases (ROG) emissions in the region, contributing around 20 percent of NOX emissions and 25 percent of ROG emissions from all anthropogenic sources in Los Angeles County in 2015. The longitudinal data also suggests significant emission disparities between vehicles registered in socioeconomically disadvantaged communities and those registered in non-disadvantaged communities in the Los Angeles area.

In order to effectively reduce air quality disparities across communities for enhanced environmental justice, CARB needs a substantial set of vehicle emissions data throughout California, especially those reflecting real-world driving conditions such as RSD measurements. The proposed study will enable continued monitoring of the fleet emission trends as vehicles certified to CARB's Low Emission Vehicle II (LEV II) emission standards advance to older ages, and quantify the extent to which total fleet emissions are attributable to older, more emissive, vehicles. The study will provide substantial statewide vehicle emissions data. This data will help us understand air quality disparities across communities resulting in enhanced environmental justice. The collected RSD data will inform CARB's mobile source emissions inventory as required by the California Health and Safety Code, the California Clean Air Act of 1988, and the Federal Clean Air Act of 1990. The collected information of on-road zero-emission vehicles (ZEVs) can help gauge the ZEV ownership penetration and usage in disadvantaged communities as a result of California's substantial ZEV-purchasing incentive funds for lower-income households under CARB's Clean Vehicle Rebate Project and Enhanced Fleet Modernization Program. In addition, this study will provide data to help evaluate air pollution impact of Smog Check program attributes.