Cities with decent public transport spine, short travel distances emit a lot less toxic pollutants

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Excerpts from the report “The Urban Commute: And how it contributes to pollution and energy consumption”, by Anumita Roychowdhury and Gaurav Dubey, Centre for Science and Environment, New Delhi, which seeks to rank 14 Indian major cities:

Cities that have a decent public transport spine, compact urban form, short travel distances, lesser number and usage of personal vehicles, and lesser vehicle miles travelled, emit a lot less greenhouse gases and toxic pollutants and consume less energy. If these parameters that influence emissions and energy use are not properly understood, reducing emissions and energy consumption from urban travel will become increasingly difficult.

Bhopal ranks best—advantage of early action

Bhopal is among the eight metropolitan cities ranked along with six megacities. It obviously has an advantage in terms of lower population, and much lesser vehicle numbers and vehicle miles travelled compared to the megacities, but among the metropolitan cities of Jaipur, Kochi, Lucknow, Hyderabad, Vijayawada and Pune, it holds other advantages. Even though its personal transport usage is higher, its 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. Vehicle numbers are also among the lowest. This has given Bhopal an edge over other cities.

Bhopal has taken early action to improve its public transport usage—its city bus system (that already accounts for 23 per cent of modal share for public transport)—and its high share of personal vehicle trips has not eroded the advantage of its compactness and low vehicle miles travelled. Thus, Bhopal has the lowest particulate matter, nitrogen oxide and CO2 load from the urban commute. Bhopal has worked on building its bus and bicycle programmes with an enhanced bus fleet, a bus rapid transit system and public bike sharing schemes. Even transit- oriented development policy has progressed here.

Kolkata wins among six megacities

Kolkata ranks sixth among all the 14 cities but it wins among the six megacities and does better than even some metropolitan cities like Pune and Ahmedabad. Even though Kolkata generates 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. The average distance travelled by different modes in Kolkata is lowest among all megacities. Kolkata also has the lowest vehicle stock among the megacities and second highest share of public transport. This shows that only high population, high travel volume and economic growth need not necessarily lead to higher automobile dependency. Early investment in diverse and connected public transport, and physical restraints can help.

Kolkata’s public transport culture, compact city design, high street density, short travel distances and restricted availability of land for roads and parking are among the good practices. About 60 per cent of all its travel trips are within 3–4 km. This is exactly the model that Japanese cities and Hong Kong have followed. It helps reduce overall emissions and guzzling. Kolkata has the most diverse public transport system for urban commuting—buses (now upgrading to electric buses), metro, trams, suburban rail, para-transit and waterways. If the share of public transport and para-transit are combined, they constitute 88 per cent of the total trips in the city.

Mumbai stays ahead with a solid public transport spine despite staggering growth pressures

Mumbai ranks 10th among all the 14 cities, indicating toxic and warming impacts of its urban commute. But among the six megacities, it is ahead of all except Kolkata. Given the staggering size of its population, Mumbai has the highest volume of trip generation among all the 14 cities. Average trip length of all modes is also the second highest. But average distances travelled by different modes are comparatively smaller than six other cities. Its vehicle stock is higher than Kolkata but much lower than other megacities.

Mumbai’s winning streak is a result of its public transport spine—primarily its suburban rail system. Public transport and para-transit add up to 89 per cent of all motorized trips in Mumbai. Interestingly, Mumbai has one of the highest trip length for personal vehicles and yet its overall guzzling and emissions are comparatively lower as its suburban rail, which has zero local emissions, meets 52 per cent of the travel demand in the city. Thus, despite having highest trip generation and volume of travel Mumbai could reduce negative impacts by adopting an intelligent public transport strategy.

Mumbai has also proved that economic growth need not necessarily translate into high personal vehicle dependence. Even with highest per capita GDP among the six megacities and highest volume of trip generation, use of personal modes is lowest in Mumbai. This has helped Mumbai to have lower emissions and guzzling compared to most other megacities.

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CO2 emission load from urban commuting in the 14 cities (in tonnes per day)

Delhi’s dilemma—ahead and yet a loser

Delhi presents a rather paradoxical case at a first glance. Most of its parameters are better than most other megacities, such as rate of trip generation, average trip length, and public transport modal share and so on. And yet, it’s the worst in terms of overall toxic emissions, heat-trapping emission and energy consumption. Delhi’s rate of trip generation is lower than Kolkata, Mumbai, Chennai and Bengaluru. Delhi’s average trip length for different modes is lower than Chennai, Mumbai, Bengaluru, Vijayawada, Kochi, and Hyderabad. Delhi’s public transport share is the third best among all cities. Delhi is seventh in per trip pollution generation. Despite these relatively better overall stats, why is Delhi at the bottom rank?

First of all, Delhi has the highest vehicle stock among these cities. Moreover, Delhi’s per capita trip rate is comparable with Bengaluru and Chennai. (Trip rate is a function of workforce participation, unemployment, workforce participation of women, young and old persons, participation in other recreational trips, safety of travel at different times in the day and so on.) Intuitively, Mumbai comes out on top because of this. Per capita trip rate is not a bad or good thing in itself. It’s the consequences of the choices associated with those trips that need to be taken care of and regulated. So, while Mumbai has a very high trip rate, from an environmental perspective it doesn’t matter as the trips are mostly carried out on public transport, walking and cycling. (From a strict transport perspective, it does not matter if a city has a high trip generation as long as the trip lengths are short and trips happen on modes that occupy less space.

Delhi’s poor rank is an effect of its relatively higher population compared to other megacities. Delhi has the highest population among these cities. Its population in 2017 was1.25 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. This means that per day Delhi generates over 20–30 million more trips than the cities of Kolkata, Chennai, Hyderabad and Bengaluru.

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 work force. Delhi, given its huge and burgeoning population, generates more trips per day than Kolkata and Chennai combined. And, therefore, despite shorter trip length, small per capita rate of trips and so on compared to other mega cities, the total vehicle kilometres generated in Delhi far exceeds that of any other megacity. With current abysmal level of walking and public transport, it results in a massive scale of overall emissions, pollution and energy guzzling.

This 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 the other megacities. Thus, given the magnitude of the scale of the emissions and guzzling problem in Delhi, much more ambitious and harsh measures will have to be rolled out.

Chennai, Bengaluru, Hyderabad—weighed down by growth and automobility

Chennai, Bengaluru and Hyderabad bring out a different story, Chennai and Bengaluru, with large populations, have high trip generation and volume of travel. Their average trip length for different modes, particularly that of cars, is among the highest. Average trip length of cars in Chennai is the highest. Among all the megacities, the share of public transport ridership in these two cities is lower than Mumbai, Kolkata and Delhi. In these cites, the average distances or total vehicle miles traveled by different modes are among the highest. These are signs of urban sprawl that is increasing distances and dependence on personal vehicles and inciting more pollution and energy guzzling.

Though these cities have lesser number of vehicles than Delhi, they have recorded highest annual average growth rate for vehicles among all megacities. The only reason why total emissions in these two cities are lower than Delhi is due to their comparatively lower population which results in comparatively lower overall number of trips and, therefore, lesser kilometres travelled by vehicles. However, their higher trip rate, trip lengths and low modal share of public transport means that their emissions per trip are high and worse than Delhi. What this means is as the population increases in these cities and they sprawl even more, air pollution, carbon emissions and energy consumption will get far worse, leaving behind even Delhi in good time.

Hyderabad is also experiencing similar challenges. Its average distance travelled by cars and two wheelers is among the highest. Its public transport ridership is lowest among all megacities.

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NO2 emission load from urban commuting in the 14 cities (kg per day)

Cities at crossroads can turn for the better or for worse

Ahmedabad, Lucknow, Vijayawada, Pune and Jaipur are at an inflection point. Their per trip emissions are in the middle of the spectrum, and depending on what direction their mobility policies take over the next years and decades, their pollution levels may increase or decrease accordingly. They need to take corrective measures now and avoid the fate of the megacities.

Some smaller cities may have lower overall emissions due to lower volume of travel and vehicles, but may still have very unsustainable patterns of travel because of high emissions per trip due to high car usage.

Overall, Vijayawada, Chandigarh, Kochi, Lucknow and Jaipur have performed better than megacities because of their smaller population, lower volume of trip generation, lower number of vehicles and vehicular trips and shorter travel distances. But this also hides a dangerous trend in which metropolitan cities have much higher modal share of cars than noted in megacities. Share of car usage can be as high as more than 60 per cent in Pune to close to 80 per cent in Chandigarh where as in Delhi personal vehicle modal share (of cars and two-wheelers) is 22 per cent. 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 and 14 per cent in Bengaluru. This deadly combination can erode their strength. These cities need much stronger roadmaps.

Chandigarh, which is among the top performing cities for overall emissions and energy use, is one of the worst performing in terms of per-trip emissions due to very high car usage. Every time a trip is made in Chandigarh where per capita car ownership is highest, it is likely to have a much worse impact than cities with better public transport systems.


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