Sunday, March 27, 2011

Crowd behaviour

Last week, one of my friends pointed out to me that my many recent blog articles have been only on the energy efficiency topic and are not as unpredictable and/or interesting as the earlier ones. So this time am making a conscious attempt at not writing about energy. There is lot of construction activity in Bangalore and the place where I live in. The construction is not just restricted to residences but increased number of residences puts pressure on municipal corporation to provide more water and handle sewage. The road outside where we live, has been dug to lay in water and all kinds of pipes. That means our only road that gets us out of layout is closed and as is common place – a new temporary road has been found out. That road can not handle the pressures of the traffic. I was thinking about this scenario and it gave me an idea of today’s topic. Is there a deterministic (non-random) way of assessing the crowd traffic and its impact on better understanding of crowd behaviour, improved design of the built infrastructure? Crowd is being used in a generic sense and although it is about a group of people, here it is being used in a more generic sense as you would find anywhere in India – in that it is a collection of group of people, herd of cows and goats, a group of auto rickshaws, a grop of water tankers in summer and in general a group of vehicles that move in all possible directions even though the road may be straight ! If you leave in time, what is the probability in a scientific way of reaching your destination in a fixed time? Does crowd monitoring help? Let us explore.

Although crowds are made up of independent individuals or entities (remember not to leave aside the cows and buffalos and even vehicles that are driven by individuals) , each with their own objectives, intelligence and behaviour patterns, the behaviour of crowds is widely understood to have collective characterisitics which can be described in general terms. Since the Roman times, the mob rule or mob mentality is an implication of a crowd that is something other than the sum of its individual parts and that it possesses behaviour patterns which differ from the behaviour expected individually from its participants. If there is any scientific basis for the study of crowd behaviour, it must belong to the realm of social sciences and psychology, and that the mere mortals of physical sciences and engineering have limited or no business in getting involved with such studies. But I came across an article a few years ago that was interesting. It said understanding of field theory and flow dynamics is good enough to get started on getting a solution to crowd monitoring and may offer solutions that are technology based and control the crowd behaviour using developments in image processing and image understanding.

The article I mentioned above was one of IEE publications. Do not recall which one. But the thought process left an impression. It said our knowledge of study of gases can provide us insgihts into the study of understanding crowd behaviour. After all, a gas is made up of individual molecules, moving about more-or-less independently of each other, with differing velocities and directions. The ideal-gas theory provides a reasonably accurate basis of predicting the properties and behaviour of gases over a wide range of conditions, without considering behaviour of individual molecules. This was a major breakthrough and something not possible to conceive if the notion had prevailed that equations of motion for each individual molecule had to be solved in order to predict overall behaviour of a gas in any particular direction. What it also proved was an observation in mob rule, that the overall behaviour is something other than the sum total of its parts.

Now where does this similarity end? Surely the molecules of gas are different from cows and buffaloes and individuals and vehicles. They are far more complex and have a mind of their own. The theory of gases does not attribute intelligence to molecules. The possessed crowd that moves in a particular direction in a mindless pursuit is akin to the behaviour of charged particles under the influence of electric field. When you have a temporary road that is bi-directional, you not only have a crowd moving in one direction but in both and capable of inducing collisions, like particles of opposite charges.

I have known many techniques in recent years in image processing that use those well-established techniques for monitoring and collection of data on crowd behaviour. A key factor in the solutions is the use of techniques where inferences can be drawn by rising above individual pixels or objects – a notion akin to rising above molecules and individuals that make up the spaces.

Whether all of this can lead me to predict fixed time of arrival at destination is anybody’s guess. But it does provide insights into crowd behaviour and probably an interesting application of science that can make your journey to the destination enjoyable.

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