Monday, August 27, 2007

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.


  1. This is plays to one of the under-advertised strengths of hybrid vehicles such as the Toyota Prius. I don't know much about those cars, but I have seen several references to their habit of switching off the gasoline engine about 3 seconds after the vehicle comes to a complete stop, for example at a red light. Thus, no idling.

    But, part of this confuses me:
    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.

    One billion gallons of diesel does not result in 11 million tons of CO2, not directly through the (rather basic) chemistry I'm familiar with. I have not yet checked; does that Canadian website you link to explain the chemistry of fuel-to-CO2 conversion ratios?

  2. Yes, apparently the recommendation is to switch off engines if you are going to be waiting for more than about 10 seconds.

    Regarding truck idling this was my source-

    Regarding fuel chemistry-
    That particular Canadian website does not, but this does-

    In short-

    CO2 emissions from a gallon of diesel = 2,778 grams x 0.99 x (44/12) = 10,084 grams = 10.1 kg/gallon

    where 2,778 grams is Diesel carbon content per gallon

    0.99 is oxidation factor for carbon

    44/12- molecular weight of CO2 divided by molecular weight of Carbon

    So a billion tonnes of diesel will emit about 10.1 million tonnes of CO2 (not 11 million as i mentioned in the blog. I will post an edit).

  3. Ah, thanks for the clarification.

    Any recommendations on what to yell at people obnoxiously idling? I'm thinking here of the people who sit in the fire lane outside a building while a passenger goes inside for "just a second" that is invariably longer than 120 seconds. My usual rude approach doesn't seem likely to be useful.

  4. Is violence part of the Canadian way of doing things? Maybe a kick on the backside.


  5. 2 questions are there.
    One is whether we need a car? And
    Other is what is the efficiency of our engine?

    answer to the first question is city should have efficient public transportation system.

    our vehicles are running on IC engine, which has efficiency less than 25%. That means we are wasting 75% of the energy. Whether it is running or idling doesn’t matter.

    Do we need to run this inefficient engine? Is there any alternatives?

    Yes. There is. Electric motors has an efficiency of 80%. We invented it 200 years back. But still now also we are not using it in our vehicles.

    Electricity production also produces CO2. But since it is done by big power plants they incorporate sophisticated pollution control measures. Also big power plants uses turbine instead of IC engine. Turbine also has an efficiency of 80%.

    So moving to electric vehicles is the only option. But the petrol and automobile mafia does not allow this. they shows lot of ad to make people to slave of automobiles. There is a movie on this “Who Killed Electric Vehicles”.

    But we can do some small things in our life.
    1. Reduce the use petrol/diesel
    2. If possible try to use public transportation.
    3. Do not buy automobiles if possible.
    4. Buy electric vehicles
    5. Avoid air travel
    6. Live near to office
    7. Use bicycles for small distance travel.
    8. Respect pedestrian and cyclists.

    Most important:

    Do not use automobiles to show your ego.


  6. In researching this same topic for a work project I learned that the average American idles for 10 minutes each day! This makes the volume of CO2 emitted and fuel wasted even more shocking.

  7. great info... i m making a project in which i need the info about how much does a car ,truck bike or any other vehicle emit its pollution and consume fuel in one minute in indian traffic......plz provide me with statistical data with reference to india ......plz help as soon as possible

  8. Harshit-- look up my email from my profile page and email me for some resources..