Delhi's overall air quality index (AQI) is steadily rising since this morning. It stood at 397 at 10 am and 409 at 4 pm. Re-invoking curbs under Stage-III of the Graded Response Action Plan (GRAP), the Centre on Friday ordered a ban on non-essential construction work as well as plying of BS-III petrol and BS-IV diesel four-wheelers in Delhi and the National Capital Region (NCR). ?? ?

Unfavourable meteorological conditions including fog and haze with low wind speed are the major causes for a sudden spike in Delhi's daily average air quality index (AQI), the Commission for Air Quality Management (CAQM), a statutory body responsible for formulating strategies to combat pollution in the region, said in its order.

The Delhi transport department in its order said, the sub-committee for operationalisation of the revised GRAP has reviewed the air quality scenario as well as the forecast for meteorological conditions and air quality index in Delhi.?

"As per directions as provided under Stage III of the revised GRAP and under Section 115 of Motor Vehicles Act, 1988, it is hereby ordered that there shall be restrictions to ply BS-III petrol and BS-IV diesel LMVs (four-wheelers) in NCT of Delhi with immediate effect till further orders (except for vehicles deployed in emergency services, police vehicles and government vehicles used for enforcement)," the order said.

"If any BS-III petrol and BS-IV diesel LMVs (four-wheeler) found plying on road will be prosecuted under section 194 (1) of the Motor Vehicles Act, 1988, which provides with a fine of Rs 20,000," it said.?

Under Stage-III, restrictions are also imposed on the operation of BS-III petrol and BS-IV diesel four-wheelers in Delhi, Gurugram, Faridabad, Ghaziabad, and Gautam Budh Nagar. The GRAP is the Centre's air pollution control plan implemented in the region during the winter season. ?? ?

The GRAP categorises actions into four stages: Stage I - ''Poor'' (AQI 201-300); Stage II - ''Very Poor'' (AQI 301-400); Stage III - ''Severe'' (AQI 401-450); and Stage IV - ''Severe Plus'' (AQI>450).