“Congestion is a market response to a place being good”: A Talk By Dinesh Mohan

By Dinesh Mohan | 16 January 2016

Dinesh Mohan retired as Emeritus Professor at the Centre for Biomedical Engineering at the Indian Institute of Technology, Delhi in 2015. He was previously the Coordinator of the Transportation Research and Injury Prevention Programme at IIT Delhi. He is a recipient of the Distinguished Alumnus award from IIT Bombay and the International Distinguished Career Award from the American Public Health Association. Mohan’s research has been on transport, human tolerance biomechanics, motor vehicle safety and road traffic injuries.

On 21 December 2015, Harper Sutherland, an intern at The Caravan attended Mohan’s talk “Thought Experiments in Moving around Cities” at the India International Centre in Delhi. He discussed the argument for limiting road space for traffic, the importance of congestion and the lack of accurate data regarding pollution and motor vehicles.

The situation we face in Delhi today is horrible pollution. And we start by comparing Delhi to Singapore, to New York, and to many other cities which are on the coast. If you’re going to compare Delhi with any other large city, you’ll have to compare us with other landlocked cities. Because landlocked cities’ air, and what happens in those landlocked cities is very different from cities on the coast. Or with very, very large rivers around them.

The problem is that when you look at traffic, you think of it as just vehicles moving from one place to another. But actually, traffic has a huge amount of effect on our health. Congestion is the least of our problems. Congestion is a market response to a place being good. The reason places get congested is—that’s where people want to go. You should be really happy that a place is congested. If it is not congested, then no one wants to go there.

So coming back to the pollution in Delhi: how do we calculate what is causing pollution in Delhi? There are two approaches for finding out what is happening. One is a bottom-up one, and the other is top-down. Bottom-up is a source inventory, in which you take everything that causes pollution, so you have vehicles, stationary generator sets, bulldozers, cooking sources, power plants, brick kilns, fires, road dust, etc. Then you find out how many of those are there in the city. What’s very interesting is we don’t know the exact number of vehicles being used in Delhi. Fires; we say “don’t burn this, don’t burn that.” We don’t know how many fires come out in the evening. We say, “you’re not allowed to burn wood or leaves.” Then what is the chowkidar going to do; do you give him a heater to sit the whole night? So we have the Supreme Court and other courts, and administrators just adding edicts, that you can’t do this, you shouldn’t do that, without finding a solution. That’s why it doesn’t work. Our calculations for road dust for road dust are also rough approximations. We have very rough estimates for all of this.

And the top-down method is a chemical analysis of particulates (a mixture of extremely small particles and liquid droplets including acids such as nitrates and sulfates, organic chemicals, metals, and soil or dust particles) in the air. We collect particulates in a sampler, which is a very sophisticated procedure, for analysis. We look at all the chemicals in the particulates, the chlorides, nitrates, sulphates, etc., all the different kinds of carbons, and all the trace elements. We have some idea on what produces what combination of these different kinds of carbons and trace elements. So that if this group of trace elements is in this particular number of particulates—we can identify what comes from internal combustion engines, what comes from wood burning, what comes from power plants, etc.

Very few laboratories in India at present can do this, because some of the units (the samplers) which were donated, quit working after six months. So some of the people who do this kind of analysis send particulate samples to the US or UK to have it analysed. So as of today, there are only two reliable studies on air pollution. One is from bottom-up, and the other is from top-down. So how do we find out? We have to find out how many vehicles there are in the city.

It turns out that no vehicle ever gets removed from the RTO’s (Regional Transport Office) records. So the number of vehicles in India, in Delhi, or in every other city, is a cumulative number for the last 50-60 years. It is not possible to have nine million registered vehicles in Delhi. There are only 3.5 million families. Which means that there are supposedly three vehicles per family in the poorest country in the world. I don’t see how any sensible human being can believe that number! So what we did is, we went and sampled. We went to petrol pumps randomly, and we sampled vehicles going to them, got the average age profile of the vehicle. We know how many were sold last year, then we calculate. In Delhi, motorcycles and other two-wheelers are 45 percent of the official number of vehicles on the road. And cars are 51 percent of the official number. And to find out if this is true, we did a study in Rajkot, and we got similar numbers. So roughly, the total number of vehicles in Delhi is half the official number. Then what is the age of vehicles? We took the sample, and so we know the number. 68 percent of the cars in Delhi are less than 5 years old. And 26 percent are less than 10 years old. And only 1 percent is more than 15 years old. And here we are so excited about banning vehicles more than 15 years old!

Based on these numbers, Professor [Sarath] Guttikunda (an independent researcher at UrbanEmissions.Info who has studied urban air pollution) went out and found out what is happening around the city. So an actual survey was done, which is possible by looking at aerial photographs. Where the power stations are, etc., and based on that, we start modeling. This is all based on rough estimates because no one in Delhi knows what a vehicle emits. The numbers we have for vehicle emissions are what was done when they were tested—not what they are doing on the road. No one knows what a CNG (compressed natural gas) bus emits. No one knows what a CNG auto emits. What we had to do was to take numbers from when they were tested, and you calculate new numbers based on ageing. Professor Guttikunda did that, and this is what we got. As far as particulates were concerned, 2.5 (micrometers in diameter), two-wheelers emit 8 percent, four-wheelers 19 percent, and three-wheelers 1 percent of the particulates. What is interesting is every day you read in the newspapers, that some people have said, “Motorcycles emit more than cars.” Absolutely unscientific! This is the best estimate. I won’t even say this is absolutely accurate, but it is the best estimate in Delhi today.

And what we are completely ignoring is nitrogen oxide. Nitrogen oxides are not produced by the use of fuel. Nitrogen oxides are produced when you heat air. Because there’s nitrogen in the air and oxygen in the air. So when you heat air, the two combine, making nitrogen oxide, and when it goes up in the air, it forms nitric acid. It also forms particulates, and it is terrible for you, but what’s interesting is that nitrogen oxides are produced by buses, three-wheelers, and heavy vehicles, because they’re running on CNG. Is anyone talking about what CNG is doing? They don’t produce particulates, but they produce much more nitrogen oxide than petrol vehicles. So does diesel. But only diesel is discussed. Because CNG is the magical solution that Delhi did; we can’t talk about it! So that’s what we’ll have to do, to go out and measure what is happening.

So these are the two problems. There are these two estimates, Guttikunda’s estimate and Pallavi Pant (a researcher who has studied the contribution of road traffic to particulate matter in the UK and in Indian cities), who’s only done the chemical analysis until now. We are told that there is an IIT Kanpur study which the government commissioned. The Delhi government recieved that report two months ago. It has not been released; it’s secret. Can you image, something which the people have paid for, from tax money, is secret? Why is it secret? We can’t get it. When the professor at IIT Kanpur was contacted, to obtain a copy of the report, he said no, because the Delhi government has said that it is at the draft stage and can’t be released. The IIT Kanpur report also supports these numbers, and that’s why it is secret. And it is a government report, commissioned by the government. How can you take decisions when reports are kept secret? My suspicion is that the IIT Kanpur report is pretty good because I think they have done both the calculations, the chemical and the bottom-up. So what happens now?



This lecture has been edited and condensed.

Dinesh Mohan retired as Emeritus Professor at the Centre for Biomedical Engineering at the Indian Institute of Technology, Delhi in 2015


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