Black Friday Disaster Scenario

• Electronic store selling 9th gen game consoles at massive discount
• Three per person limit creates arbitrage opportunity (hundreds of dollars profit)
• Mass of people fills pedestrian mall width, growing before 9 AM opening
• Security arrives 8 AM, announces only 500 consoles available
• Crowd refuses to form orderly line
• Security lets small groups in from front
• 30 minutes later: predictable crowd crush occurs
  • Back of crowd pushes forward (concerned about dwindling supply)
  • Core gets compacted, individuals lose movement ability
  • People get asphyxiated from compression
  • Three groups with different incentives: back wants consoles, security keeps crowd out, core wants to survive

Debunking Traditional Crowd Psychology

• Antiquated view: mass gatherings devolve into mindless state, dehumanize individuals
• Recent research dispels this notion
• In emergencies, people do exact opposite of selfish behavior
• Of 21 major crowd crushes this decade, only 2 involved people running from deadly threat
  • Yemen: electrical explosion
  • Egypt: church fire worshipers fleeing
• Counter-intuitive: running from fire stronger incentive than buying console, yet lower crush frequency

Identity and Cooperation in Crowds

• Flight example: normal flight = no interaction, delayed flight = cooperation emerges
• Canceled flight = even more cooperation (sharing rental cars)
• Explanation: shared identity concentrates during distress
  • Normal: weak "traveler" identity
  • Delayed: strong "distressed traveler" identity
• Greater shared identity = greater cooperation
• Study: London Underground simulation - participants more likely to help person wearing their team's jersey
• Most events involve shared identity (fans, religious followers, protesters)

Evacuation-Based Crushes Rarity

• London Underground bombings 2005: victims showed perceived unity, selfless cooperative behavior
• High degree of crowd cooperation in disasters, leading to orderly crush-free evacuations
• Civil unrest crushes also rare
• Only major riot crush this decade: 2022 Kanjuruhan Stadium, Indonesia (caused by police tear gas, not riot itself)
• Last major riot crush: 2016 Ethiopia protests (also police intervention)
• Riots feature low competitiveness, strong shared identity = low crush potential

Hajj Pilgrimage Analysis

• 2+ million Muslims descend on Mecca annually
• Strong shared identities: Muslim + Pilgrim + state of Ihram (ritualistic purity)
• Yet home to 20th and 21st century's deadliest crowd crushes (1000+ dead each)
• Study of Kaaba prayer areas:
  • Plaza: best unobstructed view, equal experience
  • Balconies: pillars obstruct view, variable experience based on pushing/shoving
• Balconies showed lower crowd cooperativeness
• Key finding: competitiveness up = cooperativeness down

Concert Venue Crush Scenarios

• Predictable scenario: people spend money on tickets, arrive at stadium, event starting but still outside
• Examples of this dynamic:
  • 2023 San Salvador, El Salvador
  • 2022 Yaoundé, Cameroon
  • 2019 Antananarivo, Madagascar
  • 2017 Luanda, Angola
• Unassigned seating creates competition for best view
• Bands and fans prefer unassigned floor seating (high energy, dynamic) over assigned seats (boring, clinical)

The Who Concert Disaster 1979

• December 3, 1979, Cincinnati Riverfront Stadium
• 18,348 unassigned seats sold out
• Competition for best position led to afternoon lineup outside venue
• Evening arrival, crowd grew cold waiting
• Only 2 doors opened for nearly 20,000 people
• Late sound check mistaken for concert start
• Push began from back, pressure felt at front
• 11 dead, dozens injured
• Aftermath blamed character, substances, rock culture
• Real cause: bad design - understaffed security, only 2 doors for 20,000 people
• At 5+ people per square meter: individuals lose movement control, fluid dynamics principles apply

Post-Who Disaster Changes

• Cincinnati banned general admission concerts 1979-2004 (24.5 years)
• US cities adopted stricter event regulations
• National Fire Protection Association rethought life safety codes
• Today: most seats assigned, unassigned heavily monitored
• Entry/exit strategies heavily planned, redundant, practiced

Recent Near-Misses and Incidents

• 2020 European Football Championship, Wembley Stadium
  • 2,000 ticketless England fans forced entry
  • 6,000 additional fans ready to charge if England won
  • Event on "razor's edge" of deadly disaster
• January 2023 Sheffield Wednesday playoff game
  • Fans packed into narrow concourses
  • Turnstiles opened 30 minutes early
  • People hoisting crying kids to relieve pressure

AstroWorld Festival 2021

• Houston Energy Park, designed for 200,000 people
• Capacity lowered to 50,000 by fire chief
• Two-stage layout expected crowd dispersion
• Secondary stage music ended, Travis Scott delayed primary stage start
• Crowd shifted from west to north stage
• Barricades created effective corral
• All 10 deaths occurred in this quadrant
• Bad timing + bad barricade configuration

Saudi Arabia's Hajj Infrastructure Investment

• Bridge complex existing since 1960s
• Sole conduit for millions of pilgrims from Mina tent city to Jamarat pillars
• 2004: 251 pilgrims died, Saudi government altered pillar walls
• 2006: 345 died on bridge entry ramp
• $1 billion reconfiguration:
  • Bridge widened by 260 feet (80 meters)
  • 4 additional floors added
  • Massive sun awning
  • Capacity: 500,000+ pilgrims per hour
• Nearly 2 decades later: bridge handles growing crowds successfully

2015 Mina Stampede

• Worst Saudi crowd crush ever: estimated 2,400 deaths
• Location: intersection of pedestrian streets 206, 223, 204
• Simple T-intersection choke point
• Hours away from impressive crowd control infrastructure
• Problem relocated to infrastructure's nearest weak point
• Became geopolitical issue, deteriorated Saudi-Iranian relations

Modern Hajj System Success

• After 2015 disaster, Saudi Arabia invested heavily in safer, efficient system
• Combines infrastructure, technology, psychology
• Modern Hajj perhaps most organized event in world
• Accident-free since 2015 crush

Risk Mitigation Principles

• Prediction easier in retrospect
• For every deadly crush: countless successful rowdy events
• People love risky situations
• Key difference: proper planning to mitigate crush potential
• Three critical steps:
  1. Knowledge of risk factors
  2. Ability to identify when things get out of control
  3. Ability to respond appropriately
• Almost every incident involves failure of one of these steps
• Culpability for why crushes occur is almost inevitably predictable