The Union Cabinet on Wednesday (June 3) approved a two-year clean mobility scheme to reduce air pollution in the Delhi-National Capital Region (NCR) that will incentivise replacement of older trucks and buses with BS-VI or stricter emission-compliant vehicles. Government vehicles will be excluded from this scheme.BS refers to Bharat Stage, a set of emission standards to regulate and reduce vehicular air pollution. While BS-IV regulated tailpipe pollutants like nitrogen oxides (NOx), carbon monoxide (CO), and particulate matter (PM), BS-VI introduced stricter limits on such tailpipe emissions besides pushing cleaner fuels and advanced onboard diagnostics.There have been Union government and Delhi government schemes introduced and implemented in the past few years to incentivise a transition to electric vehicles or BS-VI vehicles, including for buses, such as the PM-eBus Sewa. The new scheme, however, specifically targets BS-IV vehicles as well as older trucks and buses compliant with BS-IV emission norms in Delhi-NCR.The scheme is likely to benefit 2.07 lakh (1.91 lakh trucks and 16,329 buses) owners in Delhi-NCR, said a government statement on the Cabinet decision. While scrapping is mandatory for BS-III or older vehicles, BS-IV vehicles may either be scrapped or sold outside NCR, only in places which are not covered by the National Clean Air Programme.Delhi-NCR suffers from extreme air pollution and the predominant sources of pollution are transport sector, dust, industrial pollution, and biomass burning. These sources are both local as well as regional within a broader geographical airshed.The contribution of these sources, though, varies depending on the season, as meteorological factors play a crucial role in saturation or dispersal of pollutants.Vehicular emissions remain a key concern as Delhi-NCR’s vehicle fleet is high at 2.98 crore vehicles and it is growing at 7% per annum, as per government data. Earlier this year, a meta-analysis of multiple emission source apportionment studies from 2015 and 2010 by a panel of air quality experts attributed 23% of winter PM2.5 pollution and 19% of summer PM2.5 emissions to the transport sector. This expert panel was tasked by the Commission for Air Quality Management (CAQM) in Delhi-NCR to assess reasons behind the worsening of air quality in the region.Story continues below this adAlso in Explained | You saw Churu dust storm videos. Aravallis protect Gangetic plains from that, but shield is weakeningOne of the most important studies on source apportionment has been the August 2018 study by The Energy and Resources Institute and The Automotive Research Association of India, which had found that the transport sector accounted for 40% of CO and 63% of NOx emissions in Delhi-NCR. Moreover, within the transport sector, trucks and buses account for 36% of PM2.5 emissions, which are lethal, fine particles that go deep inside lungs and enter the bloodstream too, causing respiratory and cardiovascular ailments.Even as the share of trucks and buses compliant with older emission norms is only 3% of the total fleet, their emission load is disproportionate to their stock. It is estimated that one pre-BS norms heavy-duty vehicle pollutes as much as 14 times of the modern, BS-VI compliant vehicles. The official government note on the Cabinet decision stated that even a BS-IV vehicle emits 2.7 times more than its BS-VI counterpart, making the transition to cleaner technology an important step to reduce air pollution.Emission potential and vehicle stockAs per official data submitted to the Supreme Court in December 2025 by CAQM, goods carrier vehicles — including light, medium and heavy goods — accounted for 4.1% of the region’s fleet as on August 31, 2025. In absolute numbers, they account for 11.80 lakh of the total 2.88 crore vehicle fleet.Buses account for only 0.6% of 1.61 lakh of the 2.88 crore fleet in the region. However, of these 1.61 lakh buses, only 34,449 are compliant with BS-VI fuel emission norms while 1,26,549 fall in the pre-BS to BS-IV-compliant category.Story continues below this adAlso read | Delhi’s pollution level has dipped. But that doesn’t mean policymakers can rest easyBS-II standards came into force from April 1, 2000, for four-wheelers and from October 24, 2001 for medium and heavy commercial vehicles. BS-III and BS-IV standards came into force from April 1, 2005 and April 1, 2010, respectively. Last year, CAQM submitted to the Supreme Court that even though a vehicle might be fit otherwise, it would still be emitting pollutants as per its BS standard, which are outdated.The CAQM-constituted panel of air quality experts had noted in their report that older vehicles, particularly those operating beyond their regulatory life, exhibit higher emission intensity due to engine deterioration and compromised emission control performance.In its June 4 press statement welcoming the Cabinet’s decision, the Centre for Science and Environment said that older, legacy vehicles lack advanced efficient emission control systems like BS-VI variants, such as diesel particulate filters and selective catalytic reduction.NewsletterFollow our daily newsletter so you never miss anything important. On Wednesday, we answer readers' questions.Subscribe“As engines age, components undergo severe wear-and-tear, causing incomplete combustion and massive release of emissions. Replacing old vehicles that met weaker emissions standards compared to the current BS-VI vehicles standards highlights the critical importance of this targeted phase-out,” CSE said.Story continues below this adIt went on to state that a single 15-year-old legacy commercial vehicle emits 11 times higher PM and six times higher NOx than a modern BS-VI-compliant diesel vehicle. An old BS-I heavy-duty diesel truck is designed to emit up to 35 times higher PM compared to a new BS-VI vehicle, CSE added.