COVID-19 alert level restrictions curtailed people’s usual activities and transport patterns from March to August 2020. This study showed that a key traffic-related air pollutant (nitrogen dioxide) was dramatically reduced during lockdown but re-bounded to higher than expected levels upon the return to Level 1. In Masterton, PM2.5 was higher than expected during Levels 3 and 2 possibly due to increased stay at home behaviour leading to more use of solid fuel heating during the cooler months.