India, Dec. 23 -- Delhi is currently under GRAP Stage IV restrictions as air quality levels continue to remain in the "severe" category, with AQI readings frequently crossing 400. As with previous GRAP escalations, vehicular movement is one of the key focus areas under these measures, which has led to confusion among owners of BS3, BS4 and even BS6 vehicles.

Under GRAP Stage IV, BS3 petrol and BS4 diesel vehicles are barred from operating in the National Capital Region. This restriction applies not just within Delhi, but across the entire NCR, including adjoining districts in Haryana, Uttar Pradesh and Rajasthan.

As per the core GRAP IV guidelines, BS4 petrol vehicles are allowed to operate in Delhi and NCR, provided they carry a valid ...