About one-third of each of Delhi’s last three winters was spent under the two strictest stages of anti-pollution curbs, Graded Response Action Plan (GRAP), according to an analysis by The Indian Express. The pattern explains why the Delhi government has decided to make several anti-pollution measures mandatory every winter – from November 1 to February 28 – instead of imposing them only during pollution spikes.An analysis of GRAP orders issued by the Commission for Air Quality Management (CAQM) alongside pollution levels over the last three winters shows that Delhi-NCR spent the majority of the November 1-February 28 period under some kind of pollution curbs.In each winter, fewer than 12 of the 120 days were free from restrictions beyond GRAP 1. Meanwhile, GRAP 3 and 4 – the most disruptive levels – remained in force for about 40 days every winter.Also Read | Vehicle, construction curbs, work from home: Delhi moves to combat winter hazeUnder GRAP 3, most of private construction and demolition activities are put on hold, while under GRAP 4, additional curbs like entry of trucks into Delhi, hybrid schooling and work from home provisions are introduced.On Wednesday, the Delhi government notified a new winter action plan making measures such as work from home, staggered office timings, construction curbs and vehicle restrictions mandatory between November and February, regardless of daily AQI levels. The government said the decision was based on air quality trends over the past three winters, when Delhi consistently recorded ‘Very Poor’ to ‘Severe’ air quality. These measures will operate alongside GRAP.Experts have criticised frequent implementation and withdrawal of GRAP.In a report released in May, the Council on Energy, Environment and Water (CEEW) said the system relies heavily on AQI levels, resulting in repeated tightening and relaxation of curbs without adequately accounting for pollution sources. It recommended a more predictable, source-based and hyperlocal approach so authorities can act before pollution worsens.Also Read | Two-wheelers constitute two-thirds of Delhi’s vehicles, why the EV policy shift matters2023-24: Consistent elevated pollutionStory continues below this adThe winter of 2023-24 saw consistently high pollution. Average PM2.5 levels were 240 µg/m³ in November, 202 µg/m³ in December and 205 µg/m³ in January before falling to 102 µg/m³ in February.During the 120-day season, Delhi spent 24 days under GRAP 3 and 13 days under GRAP 4.Unlike the subsequent winters, GRAP IV was invoked only once, but remained in force continuously from November 5 to 18 – 13 days. GRAP 3 was enforced in four separate spells as pollution fluctuated.2024-25: Highest GRAP IV daysThe winter of 2024-25 witnessed the highest number of GRAP IV days among the three seasons.Story continues below this adAverage PM2.5 levels were 248 µg/m³ in November, improving to 170 µg/m³ in December and 163 µg/m³ in January. Despite the gradual decline, repeated pollution spikes led to GRAP 4 being imposed for 27 days across three spells.The AQI in the first two weeks of November remained in the ‘Very Poor’ category, but GRAP 3 was introduced only on November 14. As pollution worsened to the ‘Severe’ category, GRAP 4 came into force on November 17 and continued into December, making it the longest period of strict restrictions in the three winters.Also Read | Pollution shift: Delhi’s air quality dashboard shows rise in Ozone as NO2, CO decline2025-26: Elevated pollution in DecemberUnlike previous winters, pollution remained high well into December in 2025-26, instead of declining after November.Story continues below this adAverage PM2.5 levels were almost unchanged between November (215 µg/m³) and December (213 µg/m³), leading to the continuation of stringent restrictions later into the season.Delhi spent 27 days under GRAP 3 and another 14 days under GRAP 4 during the season, with emergency measures extending through much of December.Why GRAP stages matterWhile GRAP 1 and 2 mainly strengthen enforcement against dust, waste burning, vehicular emissions and diesel generators, GRAP 3 is the first level that significantly affects economic activity, stopping most construction and demolition work.GRAP 4 additionally introduces the toughest restrictions, including a ban on entry of trucks into Delhi except for essential goods and services, restrictions on Delhi-registered BS-IV diesel heavy goods vehicles, curbs on public infrastructure projects, hybrid classes for students of classes 9 and 11, work from home options for government offices with only 50% physical attendance and the possibility of shutting colleges and non-essential commercial activities.Story continues below this adAccording to the CEEW report, “While GRAP formally considers forecasts, its implementation remains largely air quality index-triggered and insufficiently linked to source contribution forecasts, hotspot-level data, and pre-emptive sectoral action.”It added that GRAP mandates are “neither successive nor consistent” leading to its unreliability.“The problem is not that GRAP stages change,” the report said. “It is that frequent imposition and withdrawal without a clear source-based rationale creates uncertainty for businesses, schools, construction firms, enforcement agencies and citizens.”