impacts(3) Intervention(3) voluntary behavior change(3) Travel(3) arising(3) disease(3) reduce(3) nonpharmaceutical intervention(3) used to evaluate(3) Primary outcome(3) Efficacy(3) dimension(3) European(3) Variation(3) decrease(3) COVID(3) events(3) School(3) adopted(3) Face mask(3) Google mobility data(3) regression analysis(3) approaches(3) objective(3) lockdown(3) consequence(3) Transmission(3) Western Europe(3) NPIs(3) per day(3)