CONVERGENCE OF two large crowds of pilgrims at the entrance to the twin deck Jamarat bridge in Mecca caused the crowd crush which killed 363 pilgrims during the annual Hajj in January.
British crowd control specialists working on the Saudi government investigation into the accident said that slow moving pilgrims carrying luggage also contributed.
Around 600,000 pilgrims were involved in the crush that happened as the crowds converged on the 4 5m entrance ramp on their way to a Muslim stoning ceremony.
The ramp carries pilgrims onto the bridge which surrounds the site where three pillars are stoned as part of the annual Hajj religious festival.
Capita Symonds subsidiary Crowd Dynamics is involved in the investigation.
Chief executive Keith Still said: 'There were three factors contributing to what happened.
The first was that many of the pilgrims were carrying luggage.
'Second is that they all waited until the afternoon to do the stoning - the site is deserted the rest of the time.
'The third is the bottleneck at the start of the ramp.' As the pilgrims entered the ramp the mass of people behind them forced some of those at the front to fall over. The sheer mass of people meant that the crowd was unable to stop, so those that fell were trampled to death.
Sections of the bridge beyond the crush area were widened before last year's Hajj using Crowd Dynamics' designs in an attempt to reduce the risk of a crush.
January's disaster was the worst to hit the event for over a decade, although fatal crowd crushes have occurred regularly in recent years.
A new $1.9bn four tier bridge is being designed by Dar Consultants to replace the existing structure. It will help ease the flow of the estimated 3M Hajj pilgrims and is designed to prevent a repeat of the tragedies that have blighted the event.
The new bridge will have 12 entrances, compared with one on the existing structure. It will be designed to handle 100,000 pilgrims an hour. Demolition of the existing structure was reported to have begun this week.
The design of the new structure aims to ensure that pedestrian densities will not exceed four persons/m² anywhere within or around the Jamarat area.
Air conditioning and other such amenities will also be installed in the new 80ha site.
Construction is expected to be complete within two years.