A new report by the TRUE Initiative, based on remote-sensing testing, has revealed that commercial and compressed natural gas (CNG) vehicles are significant contributors to real-world emissions in the Delhi Capital Region (DCR). The report, titled “Real-world Motor Vehicle Exhaust Emissions in Delhi and Gurugram Using Remote Sensing,” highlights the stark difference between laboratory-tested emissions and those measured on the road, challenging the perception of CNG as a “clean” fuel alternative.
Over 110,000 vehicles, including two- and three-wheelers, private cars, taxis, light goods vehicles (LGVs), and buses, were tested across 20 sites in Delhi and Gurugram between December 2022 and April 2023. The tested fleet comprised a mix of petrol, CNG, and diesel vehicles.
Key findings indicate that vehicles produced to the latest Bharat Stage VI (BS VI) emission standards show significant reductions in tailpipe emissions compared to BS IV vehicles. For instance, real-world NOx emissions from private cars decreased by 81%, and buses showed a reduction of nearly 95%. However, for many segments, real-world emissions remain higher than laboratory limits, especially for NOx. Notably, high-use commercial vehicles emit much more NOx than private vehicles. BS VI taxis and LGVs, for example, emit 2.4 and 5.0 times more NOx than their private car counterparts.
CNG vehicles, which made up 32% of all tested vehicles, also exhibited high NOx emissions. Class II LGVs emitted up to 14 times their NOx type limit, and taxis emitted four times their limit. These findings challenge the narrative that CNG is a clean alternative fuel.
“It is evident that real-world emissions from transport vehicles differ significantly from their laboratory values,” said Amit Bhatt, India Managing Director at the International Council on Clean Transportation. “For the first time in India, we have collected significant emissions data from motor vehicles on the road. It is crucial to remember that what impacts our air quality is not the laboratory emissions, but the pollutants released by these vehicles when they are in operation.”
The report’s release coincides with the Supreme Court of India’s recent directive to implement remote sensing in the National Capital Region. Sheila Watson, Deputy Director of the FIA Foundation, emphasized the importance of this research: “This important research clearly shows India and the rest of the world that compressed natural gas is not the clean alternative fuel which was promised.”
The report suggests that policymakers in the capital region should consider stricter emission standards and accelerate the adoption of zero-emission vehicles (ZEVs). Anumita Roychowdhury, Executive Director of Research and Advocacy at the Centre for Science and Environment, India, added: “This shows that while the CNG transition has helped cut toxic particulate emissions from diesel vehicles, NOx emissions from on-road CNG vehicles without adequate controls can be high. This builds a case for the next big transition to electrification to make tailpipe emissions not cleaner but zero.”
The testing and analysis were led by the International Council on Clean Transportation (ICCT), with funding from the FIA Foundation and support from the Clean Air Fund (CAF). The research was conducted in collaboration with the Delhi Transport Department, National Highways Authority of India, and the Gurugram Administration.
