http://friam.383.s1.nabble.com/Sounds-like-an-opportunity-tp521269p521279.html
If the luggage theory is true, how come it wasn't a trigger at previous Haj?
>
> 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
>
>
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