To combat urban challenges such as air pollution stemming from excessive vehicle use, policy makers have adopted various driving restriction policies (DRPs) worldwide. Although previous studies have extensively justified the effects of citywide DRPs on air quality, little attention has been paid to urban core-focused license-plate-based DRPs (UCLDRPs), which have gained increasing popularity among major cities. To bridge this gap, we carried out an empirical evaluation of the short-run effectiveness of Shanghai's UCLDRPs in improving air quality using difference-in-differences (DID) modeling approaches on high-frequency air quality data. The results show that UCLDRPs did not significantly improve the air quality of urban cores (the inner ring area), while worsening the air quality of surrounding zones (the 5km buffer area). The concentration of major pollutants increased by 27%-31% and Air Quality Index rose by 17% in the buffer area. Moreover, 45% of unrestricted time hours witnessed higher concentrations of pollutants including CO and PM10 after the implementation of UCLDRPs.