An Agent-Based Approach to Pedestrian and Group Dynamics: Experimental and Real World Scenarios

An Agent-Based Approach to Pedestrian and
Group Dynamics: Experimental and Real World
Scenarios
Giuseppe Vizzari1,2,3 , Lorenza Manenti1,3, Kazumichi Ohtsuka4 and Kenichiro Shimura4
1Complex Systems and Artiﬁcial Intelligence Research Center (CSAI)
University of Milano-Bicocca, Italy

2 JSPSFellow - Research Center on Advanced Science and Technology,
The University of Tokyo, Tokyo, Japan

3 Crystals
Project, Center of Research Excellence in Hajj and Omrah (Hajjcore)
Umm Al-Qura University, Makkah, Saudi Arabia

4 Research Center for Advanced Science & Technology, The University of Tokyo, Japan

Tuesday, August 28, 12

Outline

• Pedestrian and crowd simulation, a brief introduction
• Impact of groups in pedestrian and crowd dynamics
• According to the literature
• Observations at the Hajj
• A model considering the presence of groups
• The model in a simple counterﬂow scenario
• The model in a real-world scenario
• Conclusions and discussion

ATT2012 @ AAMAS 2012 - Valencia (ES) - June 5, 2012

Motivations of
crowd modeling and simulation

• Designer’s decision support
• Normal and evacuation situations
• Positioning of signs
• Malls and shopping centers
• Support the study of pedestrian
behaviour
• Envisioning of diﬀerent behavioural
models in realistic environments
• Possibility to perform ‘in-machina’
experiments
• Support crowd management by
means of the elaboration of what-if
scenarios
• Decision makers might not be experts
in crowds
• Need of eﬀective ways to visualize
simulations and analyses of results


Crowds of pedestrians as
complex systems

• Overall system behaviour depends on
individuals’ decisions and actions…
• … that are generally inﬂuenced by a
large number of factors
• … intertwined in an often
unpredictable way
• Mixed and conﬂicting mechanisms
• Competition for the shared
space…
• … but also cooperation (non
written social norms) to prevent stall
situations
• Imitation...
• ... but also natural tendency to
stay at a distance (proxemics)
• Emergent phenomena
• …


Types of approaches to
pedestrian and crowd modeling

• Particle based

• Social force model and derivatives

• Continuous space and time

• Cellular Automata

• Ad-hoc rules (e.g. Blue & Adler,
intersections) or ﬂoor ﬁeld approach
(e.g. Nishinari, Schadschneider, ...)

• Discrete in time and space

• Multi-Agent Systems

• Several approaches from computer
graphics (e.g. Thalmann, Terzopoulos,
Donikian, Manocha), some
approaches are extensions of CA, ...

• Behavioural models generally more
complex that in CA approaches


Impact of groups in pedestrian
and crowd dynamics

• Current approaches generally
consider every pedestrian as a
individual with no relationships
• Considering only his/her own
goals
• Considering other pedestrians as
moving obstacles
• Nonetheless, in several situations
pedestrians are bound by
relationships inﬂuencing their
movement
• Generally speaking, a crowd is
made up of groups of
pedestrians...
• What do we miss by neglecting this
aspect of pedestrian behaviour?


Groups in the literature -
Observations

• At least two studies report observations
about groups
• Willis A, Gjersoe N, Havard C,
Kerridge J, Kukla R, 2004, "Human
movement behaviour in urban spaces:
implications for the design and
modelling of eﬀective pedestrian
environments" Environment and
Planning B: Planning and Design 31(6)
805 – 828
• Michael Schultz, Christian Schulz, and
Hartmut Fricke. “Passenger Dynamics
at Airport Terminal Environment”,
Pedestrian and Evacuation Dynamics
2008, Springer-Verlag, 2010
• Observations carried out in low density
conditions
• Groups of small size were most frequently
observed


Groups in the literature -
Modeling and Simulation
• Extensions to the social force model
• Moussaïd, Helbing, Theraulaz et al. 2010
• Small groups (2,3,4), unstructured
• Low to moderate densities
• Validation based on actual observations
• Xu and Duh, 2010
• Only couples (groups of 2 pedestrians)
• Low to moderate densities
• Shallow validation based on data from the
literature (Daamen, 2004)
• CA models
• Sarmady, Haron, Zawawi Hj, 2009
• Leaders and followers
• Groups of 2 to 6 members experimented
• Not validated
• Agent-based models
• Qiu and Hu 2010
• Structured groups (intra and inter group
matrices)
• Large groups experimented (60 pedestrians)
• Not validated
• Group members tend to stay close to other group
members (additional behavioural component)


The Hajj in Brief

• Annual pilgrimage to Makkah,
Saudi Arabia
• Fifth pillar of Islam, a religious
duty that must be carried out at
least once in their lifetime by
every able-bodied Muslim who
can aﬀord to do so
• Over 2,5 millions of people
coming from over 150 countries
• A precise and articulated
system of rituals implying the
mass movement of pilgrims
over several sites that in some
cases are about 20 km distant


The Mashaer Line

• Five proposed rail lines
connecting the holy sites with
one another and with Makkah
• The southern rail includes 9
stations: 3 in Mina, 3 in
Muzdalifah and 3 in Arafat, to
replace 35,000 cars and buses
and access the Haram and
Makkah Central Area
• Future lines to the Holy Haram
• Extend the southern rail line to
Jeddah Airport, with an
elevated alignment above the
Jeddah Expressway over an 80
Km length


Observations at the Hajj - Groups as a crowd
management organizational instrument

• Pilgrims are subdivided into groups of 250 persons
following a leader in their movement from the
nearby tents area to the platform
• The waiting boxes act as waiting areas hosting
groups waiting to use ramps or elevators
• The platform can safely host even more than 3000
pilgrims (the capacity of a train), but the process is
aimed at avoiding overcrowding of the platform


Observations at the
Hajj - Considerations

• Groups are used as an organizational
instrument to manage crowd

• Group arrival is planned,
scheduled

• Leaders decide when and where
to move, collaborating with station
officers

• Their size is relatively large, their
cohesion is not extreme...

• ... but inside them smaller sub-
groups can be identified and
they can be much more compact

• Groups have different intermediate
movement targets, although the
same final goal


Group influence in general - Considerations

• The presence of groups is pervasive in many events involving large crowds

• Groups are simply out there...

• ... it’s not a matter of deciding if they’re ‘good’ or ‘bad’ for the pedestrian
flow

• ... it’s a matter of understanding their impact, in different relevant
conditions

• The presence of groups should be carefully considered:

• Design choices might make it difficult for a group to preserve its cohesion,
which is particularly significant in certain situations (e.g. kids, elderly, mobility
impaired persons)...

• ... and this would cause stress in group members and congestions, delays
in the whole system


A model considering
the presence of groups

• Based on the floor-field CA approach,
with significant difference on movement
choice
• Employing traditional factors for
movement destination choice
• Goal orientation
• Presence of obstacles
• Presence of other pedestrians Considered factors:
(basic proxemics) + cell is closer to pedestrian's goal
+ presence of group members nearby
• We added a simple notion of group - presence of other pedestrians nearby
• A simple set of pedestrians - presence of obstacles nearby
+ random factor
• We added a factor to the movement
destination choice-making activity Movement blocking factors:
- cell is occupied by another pedestrian
• The presence of a group member
- cell is occupied by an obstacle
nearby is considered positively
• Notice that this factor alone does not
assure that a group does not split!


The model in a simple counterﬂow scenario


The model in a simple
counterflow scenario
• We can interpret the results making
considering two phenomena
1. Wide groups offer a large profile to
the counter flow, so they have a
higher probability of facing conflicts
2. Once a group has formed a line,
instead, the leader has the same
conflict probability of an individual, but
the follower has often an advantage
• In low density situations phenomenon (1)
prevails, leading to a lower average
combined flow for groups of pedestrians
whose size is larger than 2
• Pairs in fact can easily form a line,
turning phenomenon (1) to (2)
• In high density situations the probability
of facing conflicts is very high also for
individuals, so phenomenon (2) prevails,
leading to higher average combined flow
for even large groups (size 5)


Additional results -
group cohesion

• The simple cohesion mechanism can
generate different
phenomenologies

• Experiments with an extension of the
previous model (having a more
complex perception model for
pedestrians) can lead to different
situations

• Groups remain compact

• Groups split but reunites

• Groups split and cannot reunite

• A metric of group dispersion was
defined and employed to quantify
this phenomenon


Preliminary results in
the Hajj case study

• Compared three scenarios
(columns), characterized by:
• One group accessing the station
from one WB
• Two groups simultaneously
accessing the station from two
WBs
• Three groups simultaneously
accessing the station from two
WBs and from the tents area
• The diagrams respectively
show diﬀerent data for cells
• Blocks, situations in which a
pedestrian wanted to move but
couldn’t (1st row)
• Movements of a pedestrian from
the cell (2nd row)
• Space utilization (sum of the
above) (3rd row)


Conclusions and
discussion

• Groups are relevant and significant
• Models for the simulation of crowds
of pedestrians focused on collective
events should consider them
• Results of first simulations, in tune
with experiments carried out last
year in Tokyo, suggest that the
impact of groups is not so simple
to evaluate
• More observations, experiments
and simulations are necessary to
improve our understanding of the
phenomenon
• More tight collaboration between
researchers working on synthesis
and analysis of crowds (e.g.
computer vision) is promising and
possibly beneficial for both


ありがとうございます。 Giuseppe Vizzari


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