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Network Flow to Determine Protest Size

Source: http://www.foxnews.com/science/2014/09/21/new-york-climate-march-attracts-over-310000-people/

Nearly 400,000 people gathered to participate in the People’s Climate March in New York on Sunday September 22nd to attempt to influence the UN’s Climate Summit. What is often overlooked in these stories, however, is how the amount of people in the crowd is calculated. Due to protests being prone to rapidly changing, from the crowd quickly diffusing due to lost synergy or sparking due to united excitement, city planners and the media often have a very limited time window to calculate the crowd size. Without network trafficking, calculating crowd size would be more inaccurate and, in many cases, impossible.

In class, it was taught that network traffic flow can be calculated by first determining the formula for the amount of time to travel each path from some vertices A to B based off of that path’s flow. Then, through knowing the total amount of traffic navigating the graph, the amount of people traveling in each path can be calculated by assuming that people will chose a path that takes least time over a path that takes more time.

In a protest, this problem is directly a network traffic flow problem, but it introduces several complexities. To temporarily simplify matters, consider one main path from A to B—the path most of the protesters are marching on. First of all, the amount of people is not known. However, the time that the path takes to navigate can be measured; pick several people who are seemingly walking a regular pace at different times in the protest and time how long it takes for them to walk the distance. Through analyzing the effects of crowd density and the walk speed, an equation connecting the amount of time a path takes to navigate with crowd size at different times of the protest.

While this directly relates what has been discussed in class, the problem faces many different variables, such as people leaving or entering the protest at different times, groups of people gathering instead of marching, and participants making deviations from the main path. Once this problem is expanded beyond just one path, matters become much more complicated, but still, at the base, it is a networks traffic flow problem.

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