National Council of Applied Economic Research
Opinion: Sanjib Pohit
Hybrid trolley buses and trams are a way out
Calcutta’s mayor Firhad Hakim announced that reducing the city’s pollution would be a priority. A significant volume of Calcutta’s pollution emanates from the transportation sector. With India setting its net-zero emission target for 2070 Calcutta’s transportation needs to be geared towards that goal. Calcutta ranks sixth among 14 cities when it comes to overall emissions according to the Centre for Science and Environment but emerges as the least energy-guzzling and GHG-emitting megacity. Calcutta which has the most diverse public transport system for urban commuting does better than even Pune and Ahmedabad.
Of late the West Bengal Transport Corporation has been electrifying its public transport network. It procured 80 battery-operated electric buses and selected bus depots and bus terminals to support fleet operations. There are plans to increase the share of battery-operated electric buses. As a result of these efforts Calcutta received the C40 Cities Bloomberg Philanthropies Award in the ‘Green Mobility’ category in Copenhagen for the ‘Low Carbon Commute Transition’ project. It was the only South Asian city to receive this global award.
The award notwithstanding Calcutta is making a mistake by adopting battery-operated electric buses for public transportation. These undoubtedly are to be preferred over vehicles running on diesel/biofuel/CNG. But they pose some challenges. For example battery-operated electric vehicles cost more than standard buses. Since modern batteries do not power a bus for the same number of trips as those that run on fossil fuels the WBTC has to maintain nearly twice the number of electric buses. Battery life is limited: therefore the cost of maintaining a battery-operated EV fleet will be significantly higher than one that runs on CNG/diesel. Furthermore the disposal of used batteries — a hazardous material — is an issue and not much attention has been paid to this aspect while pushing for battery-operated EVs.
What would be a feasible solution then? The light railway system — the tram — is making a comeback globally. Trams have existed in Calcutta for over a century. The curtailment of tram routes seems to suggest that the city has decided that trams are not a viable option. One hears quite often that they add to traffic congestion. Truth be told most of the congestion takes place due to other vehicles encroaching upon tram routes. Trams vary from single to triple carriage cars depending on the availability of traffic space. If congestion is a problem Calcutta can operate single-carriage trams.
Hybrid trolley buses are now being adopted in many cities as they are cheaper than battery-operated EVs. In this system the electrical energy is supplied by two trolley poles. The trolleys are swivel-attached to the roof of the trolley bus and have a length of about 6m which gives the trolley bus freedom of lateral movement of up to 4.5m. Unlike the tram it does not add to traffic congestion and operates like an ordinary bus. This is a proven technology is cheaper and has a longer life than battery-based EVs.
Current trolley buses have small batteries designed to allow them to go off-wire for a fraction of a mile. In-motion charging expands this concept by equipping the bus with enough battery power for about five miles of off-wire travel. This technology is becoming increasingly popular in small Central European cities.
Ideally Calcutta should adopt this mode and depend more on trams to achieve the net-zero transition.
The writer is professor at the National Council of Applied Economic Research. Views are personal.