An Idle Threat

Part 1 of a five part series on Pune City and environment. Updated every Tuesday.

I cross Law college road everyday on my way to soccer practice. The traffic is an endless stream, and sometime back I told the other coaches that I will be coaching from the other side of the road. At the Prabhat road signal and at Nul stop the back-up is so bad, you could easily miss 3 or even 4 signals before crossing the intersection. Urban legends about these backups are growing. Just last week a woman gave birth in her car waiting for the signal. Most vehicles keep their engines idling during their wait. That gave me the idea for this blog. How much pollutants does your vehicle emit when you wait for a few minutes at a traffic signal? How much does the entire city of Pune emit?

I first had an inkling that the amounts were big when I noticed at truck stops in the U.S. that the truckers never shut down their engines. A little web research told me this astonishing fact:

Trucks in the United States consume about 1 billion gallons of diesel annually while idling! This amounts to about 11 million tons of CO2 emitted annually (Source: U.S. Dept. of Transportation). Overall the transport system in the U.S consumes 8.4 billion gallons of fuel annually while idling. This amount to about 83 million tons of CO2 emitted annually while idling.

Edit: Based on EPA chemistry of fuel combustion 1 billion gallons will emit about 10.1 million tonnes of CO2, but the EPA warns that "calculations and the supporting data have associated variation and uncertainty".

Using vehicle numbers from the Pune Municipal Corporation Env. Status Report, emission factors for various pollutants from a World Bank study and some assumptions about mileage and idling times I did some calculations for Pune. The numbers do not give any comfort.

On a daily basis, assuming a vehicle idles for just 2 minutes every day:

The total fuel consumed in Pune by idling cars, two wheelers and rickshaws amounts to an incredible 19 thousand litres per day! Emissions of greenhouse gases amount to 45 tonnes/day.

How much do all of us on an individual basis contribute? Graphs below estimates how much fuel is consumed and how much CO2, PM10 and SOx is emitted by your vehicle every year if you idle your engine for just 2 minutes every day waiting for the light to turn green.

So, if you drive a regular car you probably lose about Rs 500/- or so yearly on fuel burnt while idling. This 2 minutes is a very conservative estimate I used to do the calculations. Idling time may well be much more. For example, idling your car for 5 minutes every day, you will spend about Rs 1250 per year in fuel burnt and so on. Something to think about next time you are waiting for the light to turn green at a busy intersection. How do you make people change their habits? One way is to appeal to their civic sense, and the other in my opinion the more effective, is to make them aware of the costs of their behavior.

See, where I am going with this? If I alone spend Rs 500/- how much for the entire city? Table below shows how much the city of Pune is paying yearly in terms of fuel lost, CO2, PM10 and SOx emitted, and fuel cost for vehicle idling. This is for total number of cars, two wheelers and rickshaws in Pune, assuming an idling time of 2 minutes every day.









For readers outside India, 1 crore = 10 million, so Pune city spends Rs 34 crore or Rs 340 million worth of fuel burnt while idling. If all vehicles in Pune reduce idling time by just one minute per day we would save about 3.4 million litres of fuel worth about Rs. 17 crore annually! This is equivalent - in terms of fuel saved and CO2 emitted - to removing around 18,500 two wheelers or about 9,300 cars from the roads of Pune.

By the way, you can learn more about idling and various myths using this website from the Canadian Office of Energy Efficiency, designed specifically to help individuals, communities, businesses reduce vehicle idling and pollution.