Crowd density seen as likely cause of South Korea tragedy

SEOUL – As South Korea investigates its deadliest civilian crowd crush incident, experts say the density of people packed in a narrow and restricted alley may have reached a level that made such a disaster almost inevitable. 

Speculation has swirled on social media about who or what exactly

triggered the crush that killed 155 people in the nightlife district of Itaewon during Halloween festivities

last Saturday night.

A culprit may have been the gradual build-up of revellers that led them to be

trapped in a space where they were pressed so hard by those around them

that they had trouble controlling their body movements.

“By the time you think that you are no longer in control, it is usually too late to get out of the space because it is essentially not offering you any escape route,” said Dr Milad Haghani, an expert on crowd behaviour and emergency preparedness and a senior lecturer at the University of New South Wales in Australia.

A density of about five people per sq m may feel cramped but manageable. Once this goes to about eight to nine per sq m and beyond, the situation can become dangerous.

Dr Haghani said that once such a density is reached, the crowd becomes unstable and can lose control people are essentially helpless. Turbulence occurs on its own and does not require any misbehaviour from people in the mass.

“If one person falls at one point in the crowd, that might create a shock wave that propagates through the crowd and results in many people falling on each other involuntarily,” he said. 

Forces generated by crowd surges have been strong enough to bend steel bars, and the main cause of death is often asphyxiation.

“Crowd forces can reach levels that are almost impossible to resist or control,” wrote Dr Keith Still, an expert on crowd safety and a visiting professor at the University of Suffolk in England.

People fall against one another like dominoes and the forces get amplified as more people go down, creating extreme pressure, he added. 

Itaewon’s bars and nightclubs are popular with foreign tourists and United States military staff, and the area started attracting revellers on Halloween about a decade ago, although such gatherings had not taken place in recent years due to the Covid-19 pandemic.

About 140 police officers were deployed to Itaewon to mark its first large-scale festivities in three years. Most of the officers were there mainly for crime prevention among a crowd estimated at about 100,000 people.

Witnesses and media reports indicate that as people squeezed into the 3.2m-wide alley, some began to fall, causing others to tumble and pile onto one another. 

The alley was located near an exit for a subway station and has been a heavily used passage for pedestrian traffic moving between a main street in Itaewon and the restaurants, bars and nightclubs on the other side.

“It was foreseen that a large number of people would gather there. But we didn’t expect that large-scale casualties would occur due to the gathering of many people,” Mr Hong Ki-hyun, chief of the National Police Agency’s Public Order Management Bureau, was quoted on Monday by Yonhap News Agency as saying. 

President Yoon Suk-yeol has called on the government to come up with crowd control systems for events like the Halloween festivities in Itaewon that do not have any specific organiser but draw masses of people.

One of the country’s biggest newspapers, The Chosun Ilbo, said in an editorial that the authorities should have had better safety measures in place, knowing that crowds would be large.

According to the Seoul Metro, a total of 130,131 passengers used the Itaewon subway station on the day of the incident, compared with 96,845 at the last major Halloween event there in 2019. 

In neighbouring Japan, about 350 officers were deployed to Halloween festivities in the nightlife district of Shibuya, which attracted about 40,000. Many were there for crowd control, including some dubbed “DJ Police” who stand on platforms with microphones and loud speakers to encourage people to abide by street safety rules.

A paper published for the Australian Institute of Criminology said a good rule of thumb is to have about one crowd control official for about every 100 people, but there is no fixed formula for allocating police and security resources at public gatherings.

With the worst of the pandemic seen as over, crowds have started to gather again, leading to some deadly incidents around the world.

These have included a rush to exits at an Indonesian football match in October triggered by the police firing tear gas that left 125 people dead.

In November 2021, there was a crush of concertgoers at the Astroworld Festival in Houston that left 10 people dead.

Crowd crushes have happened before in South Korea. In 2005, 11 people were killed in Sangju city when masses rushed into a concert venue. 

Dr Haghani advises the authorities to keep an eye online, using live videos feeds, software and professionals who can monitor crowd formations. “As soon as you see this density happening, there should be an interruption to the inflow of the people into the restricted space,” he said. BLOOMBERG