How crowd simulation software can tackle the challenges of large-scale gatherings

The Haji pilgrimage sees Muslims from across the globe descend on Mecca. In the last 19 years, Mecca has hosted an average 2,362,528 pilgrims annually. To put this in perspective, Mecca’s population as of 2019 is 2,004,888. Essentially, Mecca more than doubles in population over the six-day pilgrimage window every year. With so many people comes challenges and risks though … so, how is a mass gathering like the Hajj made possible and safe?

The stats

The number of pilgrims heading to Mecca each year steadily rose between 1999 and 2012, resulting in the highest-ever number of pilgrims in 2012 (3,161,573). This led to quotas and restrictions being placed per country by the Saudi government — and 1 million fewer pilgrims in 2013.

Despite these restrictions, risks associated with crowds remained. Stampedes had happened during the Hajj before, but the worst occurred in 2015. The resulting questions and concerns surrounding the event led to another fall in numbers in 2016 as many chose to boycott the gathering.


Numbers sharply increased after this boycott, however, and have continued to rise. It is predicted that by 2030, numbers could reach 6 million. With this in mind, how do authorities manage such a colossal number of people?

The danger of crushes

The most obvious risk and challenge of an event like the Hajj is the risk of stampedes or crushes. In such events, those present are unable to control their movements due to being pushed and lifted by pressure-ripples of a tightly packed crowd. This means density numbers need to be managed to a fine detail.

One method of managing this risk is through crowd simulation software. Maher Saleh Abolkhour from the King Abdul Aziz University used such software to analyse and predict the movement of crowds at the Hajj.

Crowd simulation

Maher focused on the Al-Masjid al-Haram, an open area space of the pilgrimage. Using crowd simulation software, Maher was able to re-run the simulation of a huge crowd in this space, recording predicted behaviour and the rise and fall of crowd density. This in turn allowed Maher to crate different models, moving gates and fences and re-running the simulation to see how these changes would affect crowd behaviour.

In terms of physical changes to the route, Jamarat Bridge, which houses the important stoning of the devil rituals, has been redesigned in recent years. In 2016, 308 escalators were installed, alongside six passenger lifts, two ambulance elevators, and two helipad elevators.

The Saudi government also has a fleet of ambulances integrated as part of their management efforts for the pilgrimage every year. According to reports by the Independent, each ambulance is considered to be its own intensive-care unit.

The Hajj is an important journey in a Muslim’s life. There have been moves to make the pilgrimage as safe as possible, from pilgrim quotas, research and simulation, and engineering. With numbers only expected to rise, it is unlikely that the Hajj will not change again in coming years.