NEW DELHI: The Commission for Air Quality Management (CAQM) on Saturday reimposed GRAP-IV in Delhi-NCR after the region’s air quality slipped into the ‘severe’ category. This comes a day after GRAP-III was enforced as a precautionary measure. The region has been grappling with high pollution levels for several months. GRAP-IV had earlier been lifted in late December.GRAP Stage IV is triggered when the Air Quality Index (AQI) exceeds 450, reaching the ‘severe+’ category. The commission clarified that measures under Stage I, Stage II, and Stage III of the existing GRAP will continue as per the modified GRAP issued on November 21, 2025.Under Stage IV, private vehicle movement is not completely banned. Restrictions are largely based on emission norms and fuel type. Vehicles meeting the prescribed standards are allowed to operate, while older vehicles face stricter curbs. BS-III petrol and BS-IV diesel vehicles are prohibited from plying in Delhi-NCR during this phase, except those providing essential services.