Same here. We've seen to many of these incidents.
I think some of the cause for these incidents is that they involve human, and there are awful lot of variations to human behavior that can be difficult to predict, or model on computers.
Thus, "dominoes" can start to fall in unpredictable directions, creating unanticipated mild surges in one area, that magnify to crushes in another area.
For example, the super crowded Meccan pilgrimage is monitored by sophisticated computers and cameras to spot potential dangerous over crowding. Organizers then make adjustments to the flow of people.
On one occasion, computers spotted a potential trouble area. Organizers then instructed pilgrims in another area not to stop to collect their day packs to avoid a jam. Day packs contained water bottles, change of shoes, snacks, sun block etc. The packs would be brought by trucks to another area where they could (in theory) be collected.
Groups from Algeria and Central Asia all obeyed the instructions. But, for many in a Bangladeshi group, disposable day packs with "extra" shoes don't exist - neither does extra money to buy more food. Rather, the packs contained all the food and other necessities they had.
The Bengalis began to stop to look for their packs, or rush ahead to get to them before they were put on trucks. This led to series of unpredicted cascading rushes in which several hundred people died as organizers struggled to contain the crowds w/o causing even more crushes.
apnews.com
