Prof. Saad A. AlGadhi, King Saud University

Prof. G. Keith Still, Crowd Dynamics

Jamarat Bridge Design Audit

(2002)

Will It Work ? Establish safety criteria and test.

Feedback comments to design team

Retest modifications

Continuous process/improvements

Establish performance

Theoretical limits

Simulations

Emergency situations

No solution without crowd management

Model of the Jamarat Bridge

Design Criteria

1. Sufficient Arrival Capacity

2. Sufficient Throwing Area

3. Sufficient Space (Density ≤ 4)

4. Sufficient Passing Area

5. Sufficient Departure Capacity

Arrival and Throwing (1 & 2) Using adesign criteria of x3 it

would require a minimum of 28m of ingress width (@ 75 p/min/meter)

Should provide a minimum of 84m of Jamarah throwing perimeter

This perimeter needs to be “effective” ie: in line of sight

Shape Tests (Criteria 2 & 3) Testing the shapes for :

Crowd Dynamics

High Density

Arrival profiles v Jamarah perimeter

Cross flows

Congestion

In situ

Angles of approach

Lines of sight

Shapes Tested (criteria 2) Circle

16, 20, 30, and 36 m

Ellipse

32x10, 32x12, 36x12, 40x14, 44x32, 46x30, 48x26,

50x22, 52x18

Deformed

16x8@8, 30x10@10, 30x10@21, 36x12@22

Validation/Confidence (2 & 3) Does the model support the

observations 74,000 Hajjis per hour (AlGadhi

& Mahmassani, 1990) 72-84,000by simulation

Sensitive to ingress width. Barriers 40-50m in use to

control flow Modelling may help planning

for next Hajj

Queue Dynamics (2, 3 & 4) Balance the system

Either increase the perimeter or reduce the ingress width

Sensitive to design changes

Further tests on new set of designs

Applies to ALL parts of the system

Isolated vs in situ (2 & 3) Testing efficiency in

isolation does not confirm optimal in situ

Angle of approach has significant effect on efficiency for ellipse

Ingress width and direction has significant effect on crowd density

New plans in test

Note: Red = high density areas

Passing area (Criteria 3) No section of the system should reduce in width relative

to the ingress width

This applies to ALL parts of the system

Dua’a areas require additional width for the Rajm process

Groups need space to assemble and regroup

Egress width (criteria 5)There needs to be sufficient egress width to

accommodate the Hajjis

This must be greater than or equal to the ingress width

Provision for normal and emergency egress

Safety – no compromises ! Is it safe ? Testing for high density and conflicts

Can it be made safer ? Design suggestions – working closely with architects

Is this the safest possible ? Crowd management and optimal design

Optimal/Safe Design Criteria (Before)

Working Together 4/5 revisions presented and tested Minor revisions

Level 1 - approved Level 2 - approved Level 4 - approved

Major revisions Level 3 - Escalators

Considerable additional work for modelling each revision 14 days – it is possible to do much more! Level 0 (ground floor) solution involves crowd

management. Can we suggest that the Jamarah perimeter be increased.

(After) Working Together

Escalators (revision 1) Major safety issues

Loose clothing

Footwear

Tripping

Over crowding

Ingress control

180 degree turns

6 levels

Is it safe ?

Best Features Added Helpers to prevent

tripping and assist throughput

Instant escape/pressure release

External screening and redirection

Managed at peak times

5.5 hours – control/rest areas for management team

Escalators (revision 4) Managed system

External screening Luggage

Mobility impaired

50% reduction in 180 degree turns

Additional space

Safe Failure designed into system

Conditionally APPROVED

Conditions of ApprovalThe system has to be managed at all times.

Switched to “stairs” at peak times

Entry screening (no luggage)

Use of escalators and elevator combinations for VIP and disabled

Requirement for 3rd floor Mina ramp

3rd floor ramp required Ramp to Mina

included

Ingress/egress ramps for future expansion

Combination escalator/elevators

Where we are now!

Spatial Utilization (Jamarah area) Utilization is a

measure of most used space divided by total available space.

Space available for management resources or cost reduction.

Assessing the capacity for each level.

Value engineering.

Throughput Working with design

team Upper limit (optimal)

Lower limited (limited by Jamarah size, queueing, safety, operations)

Cost savings possible Level 3 includes ramps

(but will vary with escalator/elevator combination)

2.6m to 3.9m Hajjis

Emergency Evacuation 5 Main towers

Helipads Elevators and stairs Simulated

+12 Minor towers Locations tested Final locations need

rechecking as design/build changes introduced

734 Hajjis per minute per tower (27m2 at 2 Hajjis per square metre)

Evacuation Rates

Jamarat within the Hajj Is the proposal safe ?

It has the capacity

Potential for future expansion

Large impact on Mina

Does it have knock on effects ?

Holy Mosque/ Tawaf

Old Jamarat Bridge discharges at ~ 148,000 per hour

What is the impact of x4 this discharge rate?

How does it fit in the master plan ?

We highlight that there is a physical limit to the Tawaf(circling the Ka’abah) due to the crowd dynamics

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New Design – 3rd Expansion

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The Northern side of the building is OPEN PLAZA areas Open plazas offer NO resistance to crowd flow

The increased capacity of the building is about threefold: From 630,000 to 1.56 million prayers

Tawaf Capacity The crowd density in Tawaf during the peak seasons

of Hajj and Ramadan reaches close to 8 p/m2.

Crowd density above 4 people per square meter (for

moving crowds) is defined as the upper SAFE limit

for crowd flow.

At 8 people per square meter the risk to the crowd is

defined as INTOLERABLE.

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Previous Studies Capacity Estimates

Studies have indicated that the capacity of Tawaf is

close to 52,000 persons per hour,

During peak times in Hajj and Ramadan the number

of people performing Tawaf ritual is distributed over

the three Haram levels as follows:

61% using Ground Floor

15% using First Floor

24% using Roof

Mataf area – Ground Floor

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Mataf area – First floor width restriction

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Mataf area – roof

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Overcrowding During Tawaf

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Proposed Circular Mataf (r=68m):Capacity = 92,400 p/hr all floors

Tawaf Modeling We developed a series of dynamic models (agent

based).

It allow us to explore what happens when we increase the number of people trying to perform Tawaf.

In this model we can explore what happens when we exceed safe density.

Agent-based Simulation Each agent is trying to move around (Tawaf) and get as

close to the Ka’abah as possible for 7 complete rotations.

After 7 rotations they leave the Ka’abah and move towards the Safa end of the Massa’a.

Agents try to get as close as possible to the Ka’abah and we can define density adverse or density seeking behaviors in the model.

The rates of stopping (for prayer or contemplation) are also an element of the agents’ behavior.

Assumptions of Agent-Based analysis Agents try to move using the following heuristic: Maximize speed. Minimize distance. Minimize time. Speeds of agents are distributed at 1.3 meter/s +/- 0.25 m/s (can be set

to any value). This is the desired speed – they slow as density increases. Agents try to get as close to the Ka’abah as possible. They circle 7 times (from the start line). They do NOT stop at the Tawaf starting line. They exit in the direction of the Sa’e taking the shortest route. Agents react to the space/other agents. The core algorithm allows the agents to see objects and avoid them; this allows one to test various configurations and assess

flow/density/capacity.

Tawaf Analysis Model ‐ 7,000 Capacity

Tawaf Analysis Model ‐ 8,000 Capacity

Tawaf Analysis Model ‐ 9,000 Capacity

Tawaf Analysis Model

To summaries the modelFlow rate determines how quickly the system

reaches its dynamic equilibrium:

Too high a flow rate and the system becomes unstable - density builds up too quickly – people near the Ka’abah experience uncomfortably high densities and cannot leave the system easily.

This in turn DECREASES throughput.

If ingress flow continues this in turn increases densities and increasing the risk of crushing.

Summary of dynamic model What is the maximum number of people performing Tawaf

that ensures safety of the crowd?

What is the maximum SAFE throughput of the Tawaf ritual on an open Mataf? On an open Mataf there is a maximum throughput ~30,000

for a sustainable, stable system in dynamic equilibrium.

It can peak (for a short time) at high throughput but is NOT stable above ~30,000 Tawaf’s per hour.

At this level the density of the crowd still reaches 8 people per square meter.

The reason for this is that at this level the risk of progressive crowd collapse and mass fatalities is EXTREME.

Progressive Crowd Collapse