The Maximum Limits of Crowd Density

How densely can crowds be packed?  This is a world-wide question, but I thought about it recently at event where I was doing crowd control.  There is a good article Crowd Risk Analysis and Crowd Safety,  from the Event Industry Association of Ireland.






I'm a member of New York City's CERT (Community Emergency Response Team), and we're volunteers that provide support to other emergency responders: if we can relieve a policeman or fireman to do more important jobs, that's a great help to them.  For example, crowd control (for certain kinds of events) is something that we are trained and can help with, along with some traffic control and management.

In the spirit of best informing me and preparing for such events, I found several resources that a consolidated to a single-sheet two-pager, including Coopers Colors of Situational Awareness, and a related Wikipedia article on Coopers Colors.

The idea of the two-pager was to combined (1) safety knowledge (EIAI article), (2) measurement/assessment techniques (estimating people per square meter), and (3) a quick assessment label with a color code scheme (adapted from Coopers Colors).,

I'd be interested in hearing others' experiences in this area. The text and diagrams below.  The pictures and notation are taken from the NYC Macy's July 4 Fireworks event in 2015, and I've served at the 2016 and this year's events.

Any thoughts?
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Crowd Conditions Situational Awareness

(adapted from Coopers Colors of Situational Awareness,
and Crowd Risk Analysis and Crowd Safety)

BE AWARE OF CROWD DENSITY, THREATS, AND POTENTIAL THREATS.  HAVE AN EXIT PLAN.

Standing Crowds are different from Moving Crowds.

Crowds greater than 5pm² standing or 3pm² in motion are dangerous.  A meter is approximately 1 yard, so 5 persons per square yard (standing) or 3 persons per square yard (moving) is the threshold density.

CONDITION GREEN: You are relaxed and the situation around you is normal.  The situation is orderly, and there is nothing needing your concern.

This picture has an orderly crowd lined up, and half the street is open available for emergency access.

  

CONDITION YELLOW: You remain relaxed, but are aware of who and what is around you.  Mentally, you are taking inventory of the people, objects, and circumstances around you.

This is a picture of an NYPD checkpoint.  Crowd density is low because you've organized the participants in a line for NYPD.

However, be on alert for people cutting the line, people asking questions, line delays (because people aren't yet ready to have their bags checked), and other possible disturbances. 

CONDITION ORANGE: You have identified something of interest that may or may not prove to be a threat. Until you determine the true nature of whatever has piqued your interest, your “radar” is narrowed to concentrate on the possible threat and will remain so focused until you are satisfied no threat exists. 

After the event is over, the outflow can start to increase from Yellow, to Orange, to Red, to Black.  Here is the Orange Condition immediately in front, but the crowd behind will be Red Condition and arriving in ~60 seconds.

CONDITION RED: If the focus of your attention in Condition Orange does something you find threatening, you will shift to Condition Red.

On the left side and immediately in front is a crowd density of 3pm² (3p/sq-m), which is the limit of safe moving crowds.

However, the further rush of the outflow pushes the density past the limit on the right side and behind.

CONDITION BLACK: Unsafe, exit unsafe condition immediately.

The crowd is now funneling through sidewalks and streets with parked cars, which increase the crowd density.  Because of the continual outflow of people, they will push, it becomes denser, and the outflow backs up into very high density.   This density of this crowd on the right sidewalk mid-block is >3pm² (3p/sq-m), which is unsafe.

ALWAYS BE AWARE OF YOUR PERSONAL SAFETY.  USE THE BUDDY SYSTEM.