The Bangkokking of Delhi

From 1998 to 2002, I worked as an economics consultant at the Asian Institute of Transport Development in Delhi, a unique institution in many ways.

Last month, its director, Mr K L Thapar, asked me to represent the institute at a UN-ESCAP conference in Bangkok. Before I left, he told me some rather hairy stories about the traffic there.

One of these was about a very senior IAS officer who got stuck in the traffic jam on his way to the airport. He had to hitch a ride on a motorcycle, all the while clutching his precious shopping in one hand and the rider's jacket in the other. Few things, you will grant, can be funnier than that.

Indian cities are rapidly becoming like Bangkok where it can take 20 minutes to travel a 100 metres. (The story is that thanks to a traffic jam, a coup was prevented, so clearly they also serve who stand and wait). Kolkata and Mumbai started down the jammy road some years ago.

Now Delhi is on its way. And while you may amuse yourself in a jam by looking out for the foreign secretary or the home secretary to whiz by on a mobike -- knowing our lads, they will probably set up a special mobike transport unit just for themselves -- the alarming fact remains: we are in for hell, expressways and flyovers notwithstanding.

The Confucian way would be to lie back to enjoy it but that does not mean it has to be on a bed of nails. There is a modicum of comfort that can be provided. However, it requires the cooperation of the authorities, mainly the police, for it to happen. In Delhi, however, their methods are crude beyond belief.

For example, at peak hours they switch off the traffic lights and go in for the old semaphoring. I have tried to explain several times to friends in Delhi police, and once even to the chief minister, why this should not be done.

R Ramchandran, a brilliant physicist who has chosen science journalism as his preferred career, explained it all to me 15 years ago when we were colleagues in another newspaper. Traffic flows, he said, are basically wave motions. Therefore, you need to know wave and perturbation theory to understand them.

Waves can have regular amplitudes. But they can also turn irregular if you perturb them in some way. While waves with regular amplitudes are 'better' than waves with irregular amplitudes, for proper regulation of traffic, there is no option but to perturb the flow. This is done by stopping one wave to allow another (cross-traffic) through.

The point of traffic lights is to keep the perturbation regular. This is, if you will, second order optimisation. If you can't go for the best, namely no perturbation, you can go for the second best, namely, perturbation at fixed intervals. That is why traffic lights have fixed timings and are synchronised. They keep the perturbation of the traffic wave constant.

Now enter Delhi police. What does the cop achieve when he switches off the lights and starts directing traffic himself? He violates the necessary condition for keeping the perturbation constant because he cannot time himself to the dot. He therefore introduces a randomness that creates chaos periodically.

This happens because when you keep introducing small disturbances at the head of the wave in an irregular manner or randomly, the amplitude of the traffic wave begins to fluctuate. And, as with ordinary wave motion, the fluctuation increases with the distance from the point of the perturbation. (To understand this, just think of a rope being flicked continuously. Even a small flick at one end can produce a large flick at the other end if you don't flick your wrist at precisely regular intervals). That is why you get pileups. The flow becomes very uneven and results in, as it were, a knotting of the rope.

There is another element to all this. It was explained to me by Dinesh Mohan of IIT Delhi, who is arguably India's leading traffic and safety expert. It has to do with the frequency with which the lights change. International experience has shown that the longest a light should remain unchanged is 45 seconds and the shortest 30 seconds. This keeps the traffic from piling up even with regular perturbation.

But what have the darlings in Delhi done? Most major lights -- now thanks to the new digital displays, you can see the time -- are set for 75 seconds and above. That extra 30 seconds is enough to clog up the space between two lights during peak hours. And that becomes a fresh source of random disturbance to the wave.

All this is very simple to understand. Why, if a journalist like me can follow it, surely the best and the brightest of Indian police also can. But, no such luck, as the following example will show. It has to do with the placement of bus stops and the optimal distance between them.

In Delhi, practically all bus stops are just after the traffic lights. When the buses stop there, they narrow the channel and thus become a third source of random perturbation.

A year ago I requested the chief minister of Delhi that the bus stops should be moved at least 500 metres away from traffic lights. She said she would see what could be done. Obviously, she was not able to persuade either the DTC or the police to "do the needful."

As for the optimal distance between bus stops, it is quite simple really. All the principles of location theory tell us that bunching of any kind should be at the middle and not at the ends.

For instance, on a beach, the best place to set up shop is the halfway point. Since very few roads in Delhi are run for more than a kilometre before reaching a traffic light, a bus stop in the middle will ensure that no one has to walk more than 500 metres to reach it. At present, it is the other way.

In the end, it all boils down to network management, which means proper switching systems, especially when the network is overloaded. The people who do this best are the telecommunications experts and railwaymen.

They know all about it because they approach it scientifically unlike the police who are given to ad hoc ways. If only the police in Delhi would consult them.

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