Sounds like an opportunity

Posted by Stephen Guerin on
URL: http://friam.383.s1.nabble.com/Sounds-like-an-opportunity-tp521269p521273.html

Gus writes:
> So, what happened? Why did the model fail, if it did?

I don't think so. Modeling for crowd dynamics can focus on:
        1) modifying physical layout
        2) modifying human behavior in the crowd
        3) modifying crowd control policies of the security personnel

>From the limited information I have on the project, they successfully modeled a
physical feature of the bridge and its modifications. Friday's tragedy appears
to be trigged by luggage brought into the event which was supposed to be
prohibited. This seems like more of breakdown in human behavior and crowd
control.  You can argue the ultimate cause was the huge densities reported of 14
people/ square meter.

>From the literate, pedestrian traffic jams start around 6 people / square meter
and get critically dangerous at 10 people / square meter. To give you a feel,
attendees at Zozobra are at about 2.5 people / square meter during the event and
reach about 6 people / square meter near the exits. Sadly, they were 2 days away
from a major reconstruction of the bridge to make it multistory and better able
to accomodate the crowds and reduce density.

On a *much* smaller scale we saw very similar factors at Zozobra. Zozobra was 1%
the event of Hajj with about 30,000 attendees compared to the 3 million at Mecca
and 700,000 approaching Jamarat bridge. At Zozobra, we made some recommendations
that were followed to minimize the densities of the crowd. We also knew that if
crowds reached expected densities on the exit bridges from the model, they would
exceed the posted bridge loading by a factor of 5. Crowd control strategies by
the police were implemented to regulate flows. An incident could have easily
happened if there was a triggering event. For example, there was a breakdown in
crowd control/crowd behavior where lawn chairs and coolers were leaking into the
event. These obstacles coupled with a smoke bomb or gun shot could have caused a
serious tragedy.

-Steve

For more information, here's a post this morning by Keith Still to the
CrowdDynamics listserve that some of us are on:

Following Pete's comments.
>Whilst this is a terrible tragedy it just brings to the forefront of
>how difficult it is to organise crowds even with all the
>improvements that have already been implemented at Jarmarat Bridge.

The Saudi's authorities put an ENORMOUS effort and for 2 days their
operation at the Bridge was facilitaing between 2 - 3,000,000
pilgrims per day.

>Fortunately improvements that have been made seemed from what I
>understand to have worked as designed and as you point out what
>seemed a minor obstacle turned into a major tragedy.

The Eastern Entrance is 45 metres wide - and fed from a plaza that is
full to capacity. I've video of the area from previous years.

To compare this to other events - a football stadium is around 70,000

There were reports that estimate some 700,000 (source Arab News) in
the Plaza area. That would be 10 footballs stadia in (approx) 49,000
square metres.

If you do the maths the figures come out at 14 people per square
metre.

Then at Noon - they all want to get through a 45m entrance.

>I  have spoken to friends who have visited Jarmarat on Pilgramage
>in previous years and they have commented on how much the safety
>has improved with the changes made.

The change from circular to elliptical Jamarah (the pillars-walls)
increased the capacity. We modelled the shape (aspect ratio) of the
Jamarah - there were no reports of accidents relating to the Pillars.

>From what they say it is the excitement and deep feeling of such a
>special place which misleads visitors into a false sense of security
>and they tend to forget their own responsibilities for their own and
>others safety.

There are behavioural and cultural issues with the crowds. Yes.

>To look at this in a risk perceptive the actual percentage injured/
>killed is still very small for such a mass gathering.

We've been collating a database of accidents and incidents - the
statistics show that. Again if anyone wants a copy of the database,
drop me a line.

>Our prayers go out to those and their families in such a tragic
>time.

It is a tradegy that touches many countries and we are all too aware
of the dangers in large crowds - our prayers to all involved in this
most tragic incident.

Regards,

Keith