Remaking Mecca

How to safely increase the capacity of the Holy Mosque? (Photo: Omar-Chatriwala/Wikicommons)

Saudi Arabian authorities have been improving walking routes in Mecca to accommodate more pilgrims and reduce risks of stampedes. Professor Serge Hoogendoorn (CEG) has been asked to advise on possible redesigns of the Sacred Mosque.

Each year literally millions of Muslim pilgrims visit the holy city of Mecca to take part in the Hajj, a once-in-a-lifetime must for every able Muslim. Currently, about 2.5 million Muslims gather for the eight-day event. In 2030, the number is expected to rise to 3.9 million, which raises serious security issues.

A notorious bottleneck was the Jaramaat Bridge (built in 1963) in Mina, where pilgrims have to throw pebbles at three pillars that symbolise the devil. Thirty years after its completion, the bridge had become dangerously outdated and overcharged by the millions of pilgrims. In the 1990s and early 2000s, hundreds of people were killed in seemingly yearly stampedes. Since 2006, however, a new bridge has been in use (built by the Bin Laden Group), with a much larger capacity. Resembling a multi-deck fly-over with three enormous walls to throw pebbles at, the Jaramaat Bridge is now the showcase of the modern-day Hajj.

“The bridge now has a capacity of 300,000 pedestrians per hour,” says Professor Serge Hoogendoorn, TU Delft’s expert on traffic flows and crowd management. “But that creates a next bottleneck at the mosque that currently has a Tawaf capacity of about 50,000 pedestrians per hour (pph).”

Inside the Al-Masjid al-Mataf or ‘The Sacred Mosque’, the pilgrims perform the Tawaf (walking seven times around the holy black bulk of the Ka’aba in counter clockwise direction), after which they also traverse the corridors between two pillars (representing two mountains)  seven times. The latter location can handle more than twice the number of people who just performed Tawaf, according to the professor.

Hoogendoorn, together with his colleague Professor Hani Mahmassani from the Northwestern University Transportation Centre (US), was asked to advise on design solutions for the mosque in terms of increasing pedestrian capacity. “Based on my empirical knowledge of pedestrian flows, I could almost calculate the capacities of different design solutions on the back of an envelope. It’s not very complicated,” says Hoogendoorn. Mahmassani’s group has made computer models and run simulations of the pilgrim flows inside the mosque. “But they had a much larger budget,” Hoogendoorn adds.

The funny thing was: both approaches yielded similar outcomes, and hence consistent advice could be given to the Saudi authorities.

In the coming months, the Saudi authorities will use the advice to develop improvements in the capacity of the Al Mataf mosque through redesign and crowd management.