While the sustained inequity in PM2.5 exposure resulting from on-road mobile sources is problematic, California's mobile source strategy has led to large aggregate reductions in emissions, exposure concentrations, and absolute disparities. Although relative disparity in exposure to PM2.5 from on-road mobile sources is effectively unchanged for Californians of color and residents of overburdened communities, the PWM PM2.5 exposures caused by these mobile sources reduced by approximately 64% for all demographic groups considered during our study. On-road mobile source controls have also reduced emissions from a broad suite of TRAPs that are also of health concern. For example, statewide on-road emissions of carbon monoxide, nitrogen oxides, and diesel PM also decreased by ~ 75% . Ambient concentrations of these pollutants have declined substantially in absolute terms, especially at sites in overburdened communities . These results speak to the value of both aggressive mobile source control and a multi-pollutant mitigation strategy that considers multiple TRAPs at once. Future mitigation efforts should continue this approach to avoid the risk of unintended consequences of single-pollutant control strategies . Despite this success, it is likely that relative disparities for other pollutants with similar spatial patterns of on-road emissions have persisted. Consider for example NOx, for which on-road sources contributed 57% of total statewide emissions in 2000. From 2000-2019, our assessment of high-resolution empirical model predictions shows a ~55% decrease in PWM NO2, but large and moderately increasing relative disparities by race-ethnicity (Fig. ).