With last year’s commitment to all in-state sales of new passenger cars and trucks being zero-emission by 2035 (California Executive Order N-79-20), California is leading the charge for transportation electrification in the United States. Despite being at the forefront of climate change management and mitigation, California has some of the worst air quality in the nation. While primarily motivated by a desire to reduce carbon dioxide emissions and reliance on fossil fuels, transportation electrification will also have a significant impact on local air quality. The goal of this study is to quantify and qualify this impact in the context of urban ozone production. From robust studies of the weekend ozone effect, we know that reductions in vehicle emissions on weekend days can actually increase urban ozone concentrations. By examining data from eight ground monitoring stations in California’s South Coast Air Basin (SoCAB) over a period of 40 years, we show that this region is a volatile organic compound (VOC)-limited system in which the weekend ozone effect is a clear trend. Additionally, these data reveal that despite a significant decline in average annual nitrogen oxides (NOx) emissions, mean ozone levels have changed very little. With this in mind, the question looking forward becomes: how will local atmospheric chemistry and air quality evolve as transportation electrification accelerates? To investigate this question, VOC-NOx ratios are modeled for varying rates of light and heavy-duty vehicle electrification in order to gauge how urban ozone production will be affected. While it is clear that vehicle electrification will ultimately improve air quality and help mitigate climate change, this study provides a unique perspective into the less understood transient impacts of electrification.

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