• Modeling the crowd

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    METRO Manila and Tacloban are bracing for a warm welcome for Pope Francis today and over the weekend. The authorities have estimated that a total of four to six million will be attending the Mass of the pontiff at the Rizal Park. This estimate is about the same volume as the number of people who attended World Youth Day in 1995.

    In such events, crowd safety is always a concern. The recent traslacion of the Black Nazarene image of Quiapo in Manila, where the crowd also swelled to around five million, has shown us the difficulties that a large crowd can bring. Last week, there were two deaths–a heart attack and a trampling amid the swarm of devotees who either did not know or care to notice their feet were killing a fellow human being.

    It is not only during religious events that such tragedies occur. We recall the Wowowee stampede at the Ultra nearly nine years ago in February 2006 where a crowd of 30,000 waiting for the first anniversary of the show grew impatient. As some people tried to get ahead of the queue, the gates were not able to hold the crowd resulting in a stampede. Seventy three people died and around 400 got injured.

    Then there is the Ozone disco fire around 20 years ago which left 162 dead. In this case, a crowd of around 390 people was jam-packed into an area approved for only 35 people. A fire broke out but the exits were not properly designed to effect the escape of customers inside.

    These events highlight that the danger in crowds is not necessarily the number of people that cause problems in the crowd but it is the density (or number of people per unit area) that one should watch out for. We also need to consider the rates at which the area fill with people as well as how fast do people leave the area of interest.

    Other concerns in crowd safety range from crowd estimation, modeling, pedestrian traffic and group behavior in large congregations. A team of my colleagues and myself from the National Institute of Physics is currently engaged in a study on crowd counting, modeling and monitoring in relation to the upcoming visit of Pope Francis. Involved in this study is Dr. Johnrob Bantang and Dr. Rene Batac together with our students and research assistants.

    We assessed current literature with regard to the safety thresholds of people per unit area, group behavior and on the exit behavior of crowds. Dirk Helbing and colleagues reported in 2007 that critical safety threshold of people per unit area based on analysis of video recordings of the annual pilgrimage in Mecca is 7 persons per square meter. Above 7 per square meter density, the individual cannot move on his own and can be crushed or brought to directions that he or she cannot control anymore.

    The rule of thumb that authorities use as basis to call an area as “full capacity” is 4 per square meter. Local density measurements of World Youth Day in 1995 have reached up to 7 people per square meter while in the 2013 Nazarene march, densities have reached up to 15 or more near the carosa.

    We also looked at how many more people can be accommodated along lanes where the Pope will pass by. We have calculated that, depending on the lanes assigned to the viewers, a kilometer of road can accommodate up to 12,000-15,000 people for a 2-meter wide sidewalk/lane. For two sidewalks on both sides flanking the road, this will amount to at most 30,000 per kilometer.

    Based on the announced route of Pope Francis in Metro Manila using Google Maps and the activities as announced by the CBCP, it is estimated that a cumulative total of about 1 million viewers will be able to see the Pontiff on Day 1 and Day 2 alone. On the fourth day, it is further estimated that about 360,000 additional viewers can be added on the roadside alone not including those who will attend the Holy Mass within the Quirino grandstand and Luneta Park.

    The team worked on limited public data. Much more can be done by directly measuring baseline values and with other observational data. In this regard, we are asking people to join in a citizen science monitoring experiment which will involve people tracking themselves using an application in their smart phones. Please visit popevisitph2015.blogspot.com for details.

    The visit of the Pope is of course much more than the crowds. It is an opportunity to have the pro-poor vicar see the actual poverty in the Philippines and for the crowds to have access to the Pope. Instead of looking at the negative side of crowd control, the government should do everything such that everyone can have access and be graced with the presence of the well-loved Pope Francis.

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