Prioritise electric buses over all other fuel types
The 2021 World Air Quality report listed 63 Indian cities in the top 100 cities in the world with the worst air quality. Motor vehicle exhaust is one of the prime reasons for poor air quality in Indian cities and research published by the International Council on Clean Transportation (ICCT) estimated that India experienced around 74,000 premature deaths in 2015 due to transportation-related pollution. Still, the amount of exhaust emanating from cars, buses, trucks, rickshaws, scooters, and other vehicles is increasing.
In this context, India’s nationwide transition to cleaner Bharat Stage VI (BS VI) emission and fuel standards on April 1, 2020, was a milestone. The leapfrog from BS IV to BS VI standards for light- and heavy-duty vehicles required coordination from all stakeholders, and is a laudable step. The most notable improvement in fuel standards was the reduced the sulfur limit, from 50 ppm to 10 ppm.
For vehicles, the new standard includes an approximately 85% reduction in the nitrogen oxides (NOx) limit, a 70% reduction in the hydrocarbons (HC) limit and, for the first time, a limit on particle number (PN) emissions. Further, to help combat the known gap between emissions reductions approximated inside a vehicle test lab and what happens in realworld driving, India will implement on-road compliance standards for buses and trucks on April 1, 2023.
These are great initiatives, but a big question is: Are the BS VI on-road compliance standards effective in their current form, or do they require a relook to capture real-world performance, in particular performance common in India’s cities?
To answer, let’s understand how on-road emissions measurement happens in the case of buses. Under the Indian regulatory framework, emissions will not be evaluated when vehicles operate at power levels lower than 20% of maximum engine power, usually at speeds less than 30 kmph.
This is the case even though the average speed of buses in cities is around 21 kmph. Similarly, emissions from the vehicle when it is not warm (coolant temperature less than 70 degrees Celsius) will not be measured. But buses operating inside a city deal with congestion and traffic signals, and given the frequent passenger pick up and drop off, they will often not be warm enough for their emissions to count. Manufacturers are also allowed to eliminate the worst 10% of emissions data from the measured data before evaluating values for compliance evaluation.
The regulation also defines the test route, and the vehicle speed ranges require that buses run at urban speeds (0 – 40 kmph) for only 20% of the total test time; the remaining 80% of the time is spent at rural (40 – 60 kmph) and motorway speeds (> 60 kmph), and this distances the test requirements from the real-world operations typical of buses.
To better understand real-world emissions performance, ICCT conducted a detailed investigation of a BS VI bus, which led its market segment in sales. Emissions were measured on three routes: (1) the test route defined in India’s current regulations; (2) a suburban route; and (3) an urban route that represented a typical public transport route in a city. The emissions from the three routes were tested based on two approaches, the regulatory approach where data was excluded as described above, and the second, where all the data was included.
The results were surprising. When following the regulatory methods, the urban route showed virtually no NOx emissions, but this wasn’t because there were no emissions. Instead, it was because all the emissions data was excluded from what counts for evaluation. In the suburban route, the NOx emission is within limits; the same is the case with the test route. However, when we didn’t exclude any data, the urban route shows more than six times the limit, the suburban route almost three times the limit, and the test route, twice the emission permitted in the standard.
For particulate emissions, the urban route has no emissions due to data exclusion, while the suburban route has insignificant emissions due to the same reason. The emission of the test route just about meets the regulatory standard; however, if all the data is included, then the test route has four times the permissible emissions while the suburban route that over three times the emission, while the urban route is barely within the limit for particulate emission.
India largely adopted its testing requirements from what the European Union (EU) implemented back in 2016, but the EU has subsequently revised its requirements to address the several shortcomings identified. To reduce the gap between what BS VI vehicles are currently allowed to emit in realworld conditions and the full potential of the BS VI technology, the Government of India should immediately consider adopting the latest standards implemented in Europe and developing its regulatory pathway to eventually eliminate this gap. Ideally, manufacturers would have to certify their vehicles using realworld emissions tests without any data exclusions. Ultimately, though, while BS VI vehicles offer large emissions benefits when compared with BS IV vehicles, for cities struggling with high pollution levels, even small additional amounts of tailpipe emissions could be dangerous.
This is a reason to prioritise electric buses over any other fuel type, especially in cities continuously struggling with poor air quality.
OUR RESEARCH SHOWS BS VI BUSES ARE GOOD ON EMISSIONS FOR
LONG ROUTE INTER-CITY OPERATIONS, BUT THEY UNDERPERFORM
WHEN IT COMES TO
CITY BUS OPERATIONS