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Delhi, Mumbai, Kolkata or Bengaluru – which megacity has the most toxic emissions?

Which cities have the highest vehicle stock? Do they also pollute and guzzle fuel the most? Or do emissions depend more on the average length of motorised trips? Check out these and more pertinent findings from CSE's latest analysis of transport-emissions in 14 cities.

Urban commuting has become one of the most energy- and pollution-intensive activities in India, contributing to increased greenhouse gas emissions, finds a diagnostic analysis of key cities of India by the Centre for Science and Environment (CSE), a Delhi-based think tank.

The study, released at a seminar in Kolkata, made an assessment of the 14 most populous cities of India based on toxic emissions of particulate matter (PM), nitrogen oxides (NOx), heat-trapping carbon dioxide (CO2), and energy consumption from urban commuting practices. These cities include Delhi, Mumbai, Kolkata, Chennai, Bengaluru and Hyderabad (henceforth called megacities); and Ahmedabad, Pune, Jaipur, Lucknow, Kochi, Bhopal, Vijayawada and Chandigarh (henceforth called metropolitan cities).

How were the cities assessed?

The CSE analysis attributed a combined score to total toxic emissions of PM, NOx, CO2 and energy consumption from urban commuting practices.

The parameters considered for understanding the differences across cities include level of motorisation, travel demand based on population, share of different modes of transport (public transport, walking, cycling, and personal vehicles), average length of daily travel trips, and quality of vehicle technologies and fuels. “If these parameters that influence emissions and energy use are not well understood and nurtured, reducing emissions and energy consumption from urban travel will become increasingly more difficult,” the study observes.

Graphic by Down To Earth

Who guzzles and pollutes more?

Delhi ranks the worst in terms of overall toxic emissions, heat-trapping emission and energy consumption.  This is despite the fact that most of its parameters are better than most other megacities, such as rate of trip generation, average trip length and public transport share.

The reasons, as the study explains, are the highest vehicle stock and relatively higher population than other megacities.

“Its (Delhi’s) population in 2017 was 1.25 times that of Mumbai, 2.5 times that of Bengaluru, 1.8 times that of Kolkata, 2.9 times that of Hyderabad and 2.6 times that of Chennai. Per day, Delhi generates around 20-30 million more trips than Kolkata, Chennai, Hyderabad and Bangalore. This is happening even though trip generation rate per person in Delhi is lower compared to other megacities due to the economic and gender profile of its workforce,” the study notes.

The analysis also reveals that the sheer effect of population, volume of travel and highest vehicle stock eclipses the benefits of having CNG, and better travel parameters than other cities, and thus Delhi comes out to be the worst in terms of total emissions per day. Delhi also has the highest vehicle stock—much higher than other megacities.

Unbridled growth weighing heavily on Chennai and Bengaluru

Owing to population boom, Chennai and Bengaluru are experiencing high trip generation and volume of travel. Its average trip length for different modes, particularly cars, is among the highest. Average trip length of cars is the highest in Chennai. “These are the signs of urban sprawl that is increasing distances and dependence on personal vehicles and inciting more pollution and energy guzzling,” the study says.

Though these cities have lesser number of vehicles than Delhi, higher trip rate, trip lengths and decreasing share of public transport in urban commuting means their emissions per trip are high, and worse than Delhi. It means, as population increases in these cities and they sprawl further, air pollution, carbon emissions and energy consumption will get far worse, leaving behind Delhi.

Why Bhopal stands out

Among the 14 cities, Bhopal emits the lowest and guzzles fuel the least during urban commuting.  Hence, the city has the lowest particulate, CO2 and nitrogen oxide load from urban commute. While lower population, much lesser vehicle numbers and vehicle miles travelled compared to the megacities work to its advantage, the city has taken early action to improve its public transport usage.

In Bhopal, average trip length of different modes is second lowest among all cities and its average distance travelled by different modes is also the lowest among all cities. One of the biggest advantages of the city, according to the analysis, is a very high share (47 per cent of all trips) of walking and cycling. It has also initiated a public bike-sharing programme.

Kolkata, Mumbai fare better than four other megacities

When it comes to overall emissions and energy consumption, Kolkata ranks sixth among all the 14 cities but emerges as the least energy-guzzling and GHG-emitting megacity. The city, which has the most diverse public transport systems for urban commuting, does better than even some metropolitan cities such as Pune and Ahmedabad.

“Even though Kolkata experiences the third highest volume of trips due to its large population, it still has the lowest average trip length for different modes because of compact urban form.

Graphic by Down To Earth

Kolkata also has the lowest vehicle stock among the megacities and second highest share of public transport. This, according to CSE, proves that early investment in diverse and connected public transport and physical restraints can help.

Mumbai is the second-best performer, with its urban mobility contributing much less GHG emission as compared to four other megacities. Given its population size, Mumbai has the highest volume of trip generation among all 14 cities. Average trip length of all modes is also the second highest. However, according to the analysis, Mumbai’s public transport and para transit add up to 89 per cent of all motorised trips in Mumbai. The city’s overall energy consumption and emissions are comparatively lower as its suburban rail, which has zero local emissions, meets 52 per cent of the travel demand.

Kolkata and Mumbai also have the lowest per-trip emission among 14 cities. This indicates a high modal share of public transport and non-motorised transport with low trip length.

Metropolitan cities setting dangerous trend

Overall emissions may be lower in smaller cities such as Chandigarh and Lucknow due to lower volume of travel and vehicles, but may still have very unsustainable patterns of travel due to high per-trip emission due to high car usage. Chandigarh is among the top performing cities for overall emissions and energy use but its per-trip emission is one of the worst across 14 cities, only behind Hyderabad.

According to the study, the share of car usage can be more than 60 per cent in Pune and close to 80 per cent in Chandigarh. These metropolitan cities have also recorded very high growth rate in vehicle registration: 15 per cent in Bhopal, 26.5 per cent in Kochi, 17.8 per cent in Lucknow and 18.3 per cent in Pune. This is in contrast to 9.9 per cent in Mumbai, 11 per cent in Delhi, 14 per cent in Bengaluru.

The CSE report sets off alarm bells as greenhouse gas emissions from transport—the third highest among all sectors—has recorded the steepest increase. On top of that, motorisation in India is happening at a break-neck speed. Initially, it took 60 years (1951-2008) for India to cross the mark of 105 million registered vehicles. But thereafter, the same number was added in just six years (2009-15).

The share of public transport at the same time is expected to decrease from 75.5 per cent in 2000-01 to 44.7 per cent in 2030-31, and simultaneously, there will be a growing dependence on personal vehicles for urban commute.

What’s the way out?

Under such circumstances, the study recommends setting time-bound targets for improving modal share of public transport and linking funding strategies with reforms in public transport sector.

Besides implementing measures for discouraging personal vehicle usage through parking policy, low emissions zones approach, and congestion pricing, both metropolitan and megacities need to integrate urban mobility strategies with clean fuels and fuel-efficient vehicle technologies.

“Cities that have a public transport spine, compact urban form, short travel distances, lesser number and usage of personal vehicles and vehicle miles travelled, emit a lot less greenhouse gases and toxic pollutants and guzzle less energy,” the study concludes.

[This article was first published in Down to Earth magazine and has been republished with permission. The original article may be read here.]

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