Mumbai tops Indian cities in road traffic CO₂ emissions per km: Study

The research analysed daily emissions from road transport across 15 major Indian cities for the year 2021, using high-resolution mapping at a 500-metre scale.

Mumbai has reportedly emerged as the Indian city with the highest road traffic carbon dioxide (CO₂) emissions per kilometre of road, a trend attributed primarily to its dense vehicle population, according to a new study published in Scientific Data.

The research analysed daily emissions from road transport across 15 major Indian cities for the year 2021, using high-resolution mapping at a 500-metre scale.

The study was led by researchers from France’s Laboratoire des Sciences du Climat et de l’Environnement and Université Paris-Saclay, with contributions from IIT Bombay and Paris-based urban mobility data firm NEXQT SAS.

The dataset is part of the CHETNA project, an initiative aimed at developing detailed, city-level estimates of carbon emissions and air pollutants for more than 100 Indian cities.

The study found a clear correlation between traffic density and per-kilometre CO₂ emissions.

Mumbai recorded both the highest vehicle density and the highest CO₂ emissions per km of road among the cities analysed.

Other cities, including Chennai, Bengaluru, Pune and Chandigarh, were also classified in a high-density, high-emissions category, though their emission levels were significantly lower than Mumbai’s. Delhi ranked in the mid-high range for per-kilometre emissions, while Guwahati, Indore and Jaipur showed comparatively lower traffic density and emissions.

While Mumbai topped per-kilometre emissions, Delhi and Bengaluru joined it as the three largest contributors to total road traffic CO₂ emissions nationwide. The study, however, noted that per capita emissions from road transport were largely uniform across the cities studied, remaining below 0.2 tonnes of CO₂ per person annually.

Beyond CO₂, the study identified nitrogen oxides (NOx) and carbon monoxide (CO) as the dominant pollutants emitted by road transport across all cities.

Larger metropolitan areas, including Mumbai, Delhi, Bengaluru, Chennai, Hyderabad and Pune, recorded significantly higher levels of these pollutants compared to smaller cities such as Guwahati, Mangaluru and Tiruppur.

In addition to road transport, emissions from residential areas, power generation, heavy industry, MSMEs and aviation are also being estimated. The data will be made accessible through a public web portal and city-specific dashboards for use by urban civic bodies.

The study has been accepted for publication in Scientific Data, a Nature portfolio journal.