Saturday, May 31, 2008

Cost of Idling

Idling is an Indian trait (like prolixity). Or so it was believed, in the old days of the 3% 'Hindu rate of growth'. Given our present rate of growth, such beliefs, at least in the West, have taken a back seat. But here I am talking of cars idling - at traffic lights, at intersections, traffic jams, things that are endemic in most major cities today. And which continues to be a problem. In a fascinating post some time back, Suvrat Kher has done a rough calculation on how much the city of Pune wastes as a result of motorised transport idling for just 2 minutes. Just to shock you into reading the article and his calculations, 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. This works out to about Rs. 500/- per year per average car owner, wasted on fuel, and taken on a yearly basis, his summary gives 7 million litres of fuel wasted correspondingly adding 16,000 tons of CO_2, 17 tons of PM10, 11 tons of SO_x to the atmosphere. The fuel cost itself is about 340 million rupees. His cost estimates are based on August 2007 prices - you need to multiply by about two and a half to get present day rupee figures. 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. Remember, all this is for just 2 minutes of idling per day for every motorised vehicle. Most of us who drive would find this number absurdly small. One could do this calculation for any of the major cities in India if the data is available. However, though its clear that the numbers are enormous, to get a better feel for the numbers, it would have been better if one could find the percentage of fuel wasted per day based on present day daily consumption. Is there a site which would have this number? Or at least the amount of fuel consumed per day in a given city? A rough and ready calculation assuming I drive for say, 30 minutes a day, would give something like a 7% loss at uniform fuel consumption (for a 2 minute idle). Since fuel consumed during driving is considerably more than while idling, this percentage is probably a slight overestimate, though compensated by the fact that most of us spend more than 2 minutes idling. Do read the post, and more important, switch off at traffic lights and long traffic jams.


AMOK said...
This comment has been removed by the author.
AMOK said...

It may be helpful to put everything in an equation before obtaining the optimal answer as "idle not". It would also be useful to understand the fractional or precentage costs, as the esteemed blogger has mentioned, what percentage are we saving? What about cost of restart - not only on the fuel consumption but the stress and strain on the vehicle starting mechanisms, which are subjected to frequent angular acceleration and thus maintenance costs? Indeed on a hot summer day, in say, Delhi, has anyone to tried to save fuel for a minute by switching off the a/c while engine-off to prevent idling? That cost makes people break out in a sweat. Additionally some vehicle do not start up really easily, if at all, once turned off -- leading to delays in traffic and the resulting cost. The answer would perhaps be to design the idle into the normal operating procedure for a vehicle, as in the hybrid. In America, as you know, proclivity for prolixity is delegated to the TV and idling to large fuel-hungry vehicles.
Read this.

Rahul Basu said...

Indeed as Omar, oops, I mean OAK has said, (and I before him) percentages would be useful though I am not sure of putting it in one equation. Perhaps someone can give it a try.

In fact, after I wrote the post, I was reminded of an earlier time, the good old days in Delhi when the only cars were the Ambassador, the Fiat and the Standard Herald in India. Most drivers were terrified of shutting of the 'injin' because all these cars were notorious for starting troubling - particularly in winter. Most DTC buses in Delhi and now MTC buses in Chennai never shut off their engines even at the terminus for fear that it wouldn't start again.

With the whole plethora of new and improved gas-guzzlers on Indian roads today, perhaps there is now little reason to not switch off, except for the Tata Indica which apparently does not start easily if you have been running with the A/C on. Indica owners will only confess this on pain of death or severe torture, no doubt out of loyalty to the brand. But I have frequently been a victim of this problem when the driver of the vehicle has been forced to confess, in the face of blatant evidence. Since Tata's are also manufacturers of trucks and buses, perhaps this idiosyncratic behaviour is built into their production line!

Rahul Siddharthan said...

I was always told not to switch on the engine for short halts, not for fear of the car stalling, but to improve battery life. Again I don't think this is a concern with modern batteries.

One issue is, switching off engine means switching off AC, and how do I make do without the AC at midday in the Madras summer? Relating to this, what about unnecessary use of AC? With my car I find that AC subtracts about 2 km/litre from mileage (admittedly it's not the newest and shiniest model). I have driven about 25000km in about 3 1/2 years. Most of this is without AC, but let's suppose that by following every possible "good driving practice" (no AC when not needed, turn off engine when idling, smooth driving, etc) I would have gained about 2 km/litre in mileage. I think this is a good upper bound, actual numbers are likely to be less. Then I would have saved about 350 litres of petrol, or about Rs 17000, in these 3 1/2 years. It doesn't strike me as an enormous saving. Of course, if everyone in the city did that the saving would be enormous, but that is about as likely as expecting everyone to turn off unnecessary lights or compost their garbage. Reducing consumption can only occur via incentives (eg, cheap and efficient public transport and high petrol prices).

AMOK said...

Respected Sire Rahul, aside from your opening phrases confusing to humble folk like this bloggerino, you have graced the comment with a fairly lucid follow-on. Perhaps a Maxwell's Demon would useful for enforcing less idling, this should be considered.

Indeed the single objective function has been optimised in one equation. They do good work at MIT, as you know, and MIT graduates are good at this sort of stuff. Here it is.

Suvrat Kher said...

I wrote that post more out of curiosity about how much fuel is being spent on idling in an Indian city, but I do agree that it is extremely difficult to change behaviour. fear of vehicle not restarting is one and then who would want to sweat it out without AC on a hot summer day? as for concerns about engine component damage due to frequent restarts offsetting savings due to reduced idling literature I came across suggests that excessive idling can also damage your engine.

Rahul Siddharthan said...

suvrat - thanks for those links. If widely known, those are more likely to persuade people to turn off their engines than appeals about the environment. (When idling, I'm often stuck behind trucks, buses, even diesel Ambassadors and Sumos, that seem to emit more black smoke in a minute than my car probably does in a year... so reducing my car's environmental impact is not uppermost on my mind.)

AMOK said...

Agreed that the on-idle state is not desirable if the off-idle state is equal in other aspects of comfort, risk, component-wear, etc. Idling to warm the engine is especially harmful. The only out from idling is public transportation, as congestion => idling. In Delhi, many taxi drivers will switch off their engines at points of predictable wait. For private car owners, it's not too popular. Imagine taking your friends out in your car for ice cream and switching it off at every light. You might seem like a miser -- or down on your luck. It is a symbol to have idling power.

Suvrat Kher said...

Sure. It is probably unreasonable to expect that people will switch off during signals due to many factors Rahul and Amok have already discussed. Hybrids or fuel cell tranport may eventually mitigate this,but I am pessimistic for the short to medium term of let's say next 15-20 years. An obvious way is expanded public transport but currently our transportation incentives favor private vehicles over public transport. you are painfully made aware of that in Pune,seeing the extreme reluctance of the administration to improve bus services.

Sunil Mukhi said...

I agree that encouraging public transportation and discouraging private is the right way to go. However, in the absence of that, there is a point I'd like to make - that idling at traffic lights is not the most wasteful thing a car driver does.

The most efficient use of fuel for a given car on a given trajectory will take place if (i) the road is smooth, (ii) the movement is smooth i.e. not interrupted by unnecessary stops and starts.

I used "unnecessary" there because stopping at a traffic light must be considered a necessary evil. What is unnecessary is a vehicle having to come to a halt because some idiot decided to take a U-turn right in its path, when he/she could have waited a few seconds for the traffic to clear.

More generally, any form of chaos-inducing behaviour is wasteful (potholes, pedestrians crossing without looking, cyclists swerving, cars barging in from side lanes...). Except for potholes, the remaining factors are due to the "instant gratification" system in place on Indian roads - you do what you want to do, whenever you want to do it. This can be conquered only with meaningfully organised infrastructure including proper crossings for pedestrians, education campaigns and - most important - significantly higher levels of training and testing before a driving license is issued.

Usually all the above is said in the context of road safety, the only thing "new' I'm saying here is I believe it will also contribute importantly to reduce fuel wastage.

Rahul Siddharthan said...

Actually, the most important thing is enforcement. It should be not too hard these days to monitor traffic with video cameras, that will automatically detect offences and either alert the cop at the next intersection or note the number. Even if it captures 10% of offenders that would be a deterrent.

Let's say the traffic police decided to
1. Paint lanes clearly on all roads
2. Mark which lanes are for straight, which for left, which for right
3. Mark, with double lines or yellow lines, places (eg near intersection) where you must stay in your lane. If you are in the wrong lane, you go to the wrong place and find your way back; you don't cut into somebody else's lane.
4. Educate, as you say.
5. Enforce.

If they could actually do this it would make a big difference. Two other peeves I have in Chennai are
1. Heavy vehicles crawling in the inner lane (I'm thinking of the IT road near our institute, in particular)
2. SUVs weaving in and out of busy traffic, hand permanently on horn.

But the traffic police don't seem bothered by any of these things. They only pull you over at an intersection if you run a red light, and only if they can catch you (so they don't get the really dangerous guys).

AMOK said...

No offence, but the image of painted lanes and people following these like sheep is more difficult to imagine than a spherical cow. Enforcement by dedicated and obedient public servants (police) is like imagining a herd of spherical cows. The lane-based (or any other solution) has to deliver immediate value to the obedient lane-philics. In other words, a smoother, faster, more relaxed ride. No amount of enforcement will make up for an overloaded, congested system, although education and reduction of wantonly chaotic events will help.

Anonymous said...

I have mentioned this before. The javascript at for comments is broken for text-mode browsers and openid. People who use the service and want the "eyeballs" of text-mode users should probably complain.

Anonymous said...

The following points do not seem to have been mentioned.

1. Synchronised traffic signals along arterial roads.
2. Emissions during starting a vehicle.

The former is probably not applicable for cities like Pune which have
not been planned with such roads in mind. Our city planners planners seem to prefer expressways and flyovers which actually encourage drivers to go faster than is optimum for fuel-efficiency. (Ever heard an auto or two-stroke two-wheeler or LPG taxi "straining to take off" on one of our spanking new expressways?).

Most of the poorly maintained vehicles that we see on our roads will be even more polluting if they were to stop their idling engines and start them when the signals change. In addition, think of the noise pollution added as everyone whose engine has started beeps everyone
in front whose engine hasn't.

In fact, we live in an upside down world so that all the modern four-wheelers that could efficiently switch off when idle do not do so since the owners want their stereo and a/c to work; at the same time the two-strokes and tempos and autos all switch off to "save fuel" and
perhaps end up polluting more than if they stayed on idle.