Safety Science 49 (2011) 286–291

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Safety Science

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Applying TRIZ principles in crowd management

Soo Chin Pin ⇑, Fazilah Haron, Siamak Sarmady, Abdullah Zawawi Talib, Ahamad Tajudin KhaderSchool of Computer Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia

a r t i c l e i n f o a b s t r a c t

Article history:Received 12 March 2010Received in revised form 12 August 2010Accepted 3 September 2010

Keywords:Crowd managementTRIZOvercrowdingCrowd disastersCrowd controlCongestion

0925-7535/$ - see front matter � 2010 Elsevier Ltd. Adoi:10.1016/j.ssci.2010.09.002

⇑ Corresponding author. Tel.: +60 016 5164535.E-mail addresses: soocp522@gmail.com (S.C. Pin), f

sarmady@cs.usm.my (S. Sarmady), azht@cs.usm.my (A(A.T. Khader).

Overcrowding that happens in places like concerts, stadiums or pilgrimage locations might sometimescause injury or loss of life. Maintaining the safety of crowd in these places is therefore very important.In addition, increasing the performance of the buildings and structures has always been an importantconcern. Most of the previous work focused on using new devices and methods for monitoring and man-agement of the crowd but they rarely focus on a comprehensive and structured approach with the pur-pose of increasing efficiency and safety. In this paper, we explore a Russian ‘‘Theory of Inventive ProblemSolving”, TRIZ, to see whether its principles can help us to solve or improve overcrowding issues. Morespecifically we find the contradictions that arise in the context of crowd management and we observewhich of the categorical solutions suggested by TRIZ might possibly be useful for our problem. Increasingthe crowd capacity in a relatively small area, which leads to overcrowding, is one of the common con-tradictions in crowd management. TRIZ has been suggested as a good method for solving problems whichinvolve contradiction and thus, chosen for this purpose.

� 2010 Elsevier Ltd. All rights reserved.

1. Introduction

Crowding happens due to gathering of large number of peoplein an area. Gathering of large crowd in places like stadiums or con-certs is positive and desirable most of the time. For example, a lar-ger crowd might produce more profit from commercial point ofview. However, excessive crowding and poor crowd managementcan lead to unwanted incidents like crushing, stampedes, injuriesand even loss of life. A lot of efforts have been put in understandingcrowd features and behaviors. Although numerous methods, solu-tions and tools have been used to solve or improve the overcrowd-ing problems but there is space for improvement in all aspectsespecially in managing crowd. In this paper, we try to look into amore fundamental issue involved in overcrowding problem. Wewill focus on finding root causes of the overcrowding problems.We will also look for structured methods of solving them insteadof just looking for new crowd management tools. TRIZ, the Russian‘‘Theory of Inventive Problem Solving” is introduced and its appli-cability in crowd management will be explored.

This paper is organized as follows: Section 2 discusses the moti-vation behind this work. Section 3 briefly explains the related workon crowd management while Section 4 describes the basic con-cepts in TRIZ. Section 5 demonstrates the possible application of

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azilah@cs.usm.my (F. Haron),.Z. Talib), tajudin@cs.usm.my

TRIZ principles in crowd management and finally Section 6 is theconclusion of the paper.

2. Motivations

Overcrowding might lead to crowd disasters and cause loss oflife and serious injuries. Several such incidents have happened inthe past. Table 1 below lists a few of the recent crowd relatedincidents.

The motivation behind this work is to explore TRIZ principles inovercrowding problem which may help to reduce the chances ofsuch serious incidents.

3. Related work

Most of the current research work in this area focuses on mon-itoring crowd as a management tool and carrying out simulationswhich help in understanding crowd behaviors. Works like Maranaet al. (1997) and Wu et al. (2006), proposes crowd estimation sys-tems which monitor and extract specific crowd information. InBoghossian and Velastin (1999), a motion-based machine visiontechnique is used to capture crowd flows and display visual infor-mation which assists CCTV operators in understanding the dynam-ics of the crowd under observation. The monitoring devices act asmanagement information systems and help in managing the crowdbut they are not always effective in reducing the overcrowdingproblem. Some studies also focus on empirical or experimental

Table 1Recent crowd incidents (Still, 2010).

Date Incidents

18th December 2005 42 Homeless people were trampled to death and 37were injured in a stampede during the distribution offlood relief supplies at a shelter in Chennai

31st August 2005 Hundreds dead in Iraq pilgrimage stampede12th January 2006 363 dead in Jamaraat Bridge when large seas of

pilgrims were moving forth to the Jamaraat at noonto perform the stoning ritual

1st January 2007 Hundreds hurt in new year revelry in Philippines4th August 2008 150 Hindu worshippers were crushed to death in a

stampede at a hill temple in northern India14th November 2009 60 People hurt in crush to see JLS at Christmas lights

event in Birmingham Not Fixed

Problem Definition

Current Situation

Causes Identification

Develop Solutions

Solution Implementation

Standardize Solution

Fixed

Fig. 1. Step by step structured problem solving process (San et al., 2009).

S.C. Pin et al. / Safety Science 49 (2011) 286–291 287

studies of pedestrian flow by means of analyzing video (Hoogendo-orn et al., 2003; Teknomo, 2002).

In addition to monitoring systems, computational and mathe-matical models of crowd can help in increasing the awarenessand knowledge on crowd behaviors. Building and structure designscan be tested to see how they perform in overcrowding situations.Several models for crowd movements and behaviors have beenproposed. Physics based models like particle, gas and fluid dynam-ics methods use physical laws to model movements of pedestrians(Helbing et al., 2001) while cellular automata and other matrix-based (Blue and Adler, 2000; Burstedde et al., 2001; Thompsonand Marchant, 1995) divide the simulation area into cells and sim-ulate the crowd movements based on the transition of pedestriansamong these cells.

Our research is somewhat different from previous works. Weaim to apply TRIZ principles in crowd management and possiblyfind alternative solutions to ease overcrowding problems (seeTable 2).

Fig. 2. Root cause searching process.

4. TRIZ problem solving

TRIZ was introduced by Genrich Altshuller and his colleagues in1946 in the former USSR. It is a set of tools, methods and strategiesdeveloped by years of research and studies over two million of pat-ents (Mann and Domb, 1999).

TRIZ is a scientific principle for solving problem and technicalinnovations but recent studies have shown that TRIZ principlesare also applicable to other fields like management (Mann andDomb, 1999; Retseptor, 2003). We have selected TRIZ as our refer-ence methodology to help with better understanding of crowdmanagement issues. In addition we hope it can help us find newideas and solutions for solving overcrowding problems. Fig. 1shows the typical structured problem solving process.

In the problem definition step, we define our main problem asovercrowding that may lead to decrease in performance and possi-bly injuries and deaths. The overcrowding issue in our case cannotbe avoided by reducing the size of the crowd. This is because

Table 2TRIZ complements structured problem solving (San et al., 2009).

Structured problemsolving

TRIZ

Problem definition TRIZ helps to define the real problem to be worked onvs. symptoms

Current situation Analysis of useful/harmful operational zones tounderstand the conflicting requirements

Identify causes Cause and effect chain helps to see other potentialcauses of problems

Develop solutions 76 Standard inventive solutions, 40 principles –identify potential solution

crowds are the most important element of an event and sometimesbig crowd is favored.

In Fig. 2, we try to find out some of the root causes of over-crowding. Through the process, we find that the overcrowdingproblem is due to insufficient expansion of the crowded areas.Expansion of the structures might not be easy because of cost con-sideration, limitation of space, retaining of the original buildingstructures and some others reasons.

After we have identified the root causes, we proceed to findingpotential solution by using TRIZ tools like contradiction matrix, 76standard inventive solutions and 40 inventive principles. Contra-diction matrix is used to resolve a conflict by recommendinginventive principles which might be helpful in creating solutionsand the 76 standard inventive solutions can be referred as oursuggestions.

5. Recommendations

Forty inventive principles of TRIZ and the 76 standard inventivesolutions will be explored and those related principles and stan-dard solutions will be discussed in this section. Besides, the trendof engineering system evolution of TRIZ has also been applied toovercrowding problem and will be discussed in the later part ofthis section.

5.1. Forty inventive principles

A fundamental concept in TRIZ is that a problem (e.g. a technicalproblem) is defined by contradictions. If there is no contradiction,

Table 3Suggested principles from contradiction matrix based on our conflicting parameters.

Principle Standard Solution

Principle 1 Divide an object into independent partsSegmentation Make an object easy to disassemble

Increase the degree of fragmentation or segmentation

Principle 7 Place one object inside another; place each object, in turn,inside the other

Nested doll Make one part pass through a cavity in the other

Principle 4 Change the shape of an object from symmetrical toasymmetrical

Asymmetry If an object is asymmetrical, increase its degree ofasymmetry

Principle 17 To move an object in two- or three-dimensional spaceAnother

dimensionUse a multi-story arrangement of objects instead of a single-story arrangementTilt or re-orient the object, lay it on its sideUse ‘another side’ of a given area

Fig. 4. Illustration of pedestrians’ segmentation.

288 S.C. Pin et al. / Safety Science 49 (2011) 286–291

this means that we can apply the standard sciences and engineer-ing to solve the problem directly. Technical contradictions in TRIZresemble the classical engineering ‘‘trade-offs”. Contradiction im-plies that an optimum state cannot be reached in a system becausesomething else or another process prevents it. A typical automo-tive example is ‘‘a vehicle which has higher horsepower, but usesmore fuel” TRIZ Journal Website. In order to solve this kind of con-flict, a contradiction matrix is needed.

Fig. 3 shows a sub section of TRIZ contradiction matrix. Therows show the worsening parameters while the columns showthe improving parameters. The cell at the intersection of columnsand rows refer to the principles that have the highest probabilityof resolving the contradiction. For example, if we want to improvespeed (parameter 9) but the shape will be worsen (parameter 12),then, according to TRIZ Journal Website, the suggested TRIZ princi-ples to solve this contradiction are:

� Principle 35 (Parameter changes)� Principle 15 (Dynamization)� Principle 18 (Mechanical vibration/oscillation)� Principle 34 (Discarding and recovering)

In the early stage of our research, we have identified that theproblem we are facing is the increasing number of people in a con-fined area. In TRIZ term, there is a volume parameter that keepsincreasing and an area parameter (for each pedestrian) that is get-ting smaller. The conflict can be resolved using contradiction ma-trix of TRIZ. We have selected volume of moving object(representing the crowd) as our improving parameter whereasthe area of moving object is the worsening parameter. The recom-mended principles from the contradiction matrix are as stated inTable 3.

The suggestion from the contradiction matrix are supposed togives us insight into possible solution for crowd managementproblems. Based on three of the four principles mentioned in Ta-ble 3, namely segmentation (Principle 1), nested doll (Principle 7)and another dimension (Principle 17), we have obtained someguiding principles which may lead us to useful solutions for theovercrowding problem. Principle 4 (i.e. asymmetry) is not used inour context because we were not able to apply in solving the over-crowding problem.

5.1.1. Principle 1: SegmentationSegmentation can be applied to the crowd problem by imple-

menting barriers to divide the crowd into different sections(Fig. 4). The barrier will avoid interference of the crowd in each

Fig. 3. Contradiction matrix (

section with the others. Segmenting the crowd may benefit us indifferent ways. A smaller crowd is easier to manage. Besides if peo-ple in one section collapse on each other, it will not affect the restof the sections. As a result, the severity of pushing and trampling isdecreased.

However segmenting of the crowd might create another contra-diction. Evacuation of people in a segmented area will be slowerdue to the increased length, decreased width and higher complex-ity of the evacuation path. This new problem can be consideredand solved using TRIZ principles. For example the segmentationbarriers can be removed during the evacuation time (refer to thenested doll principle for example) or additional evacuation pathscan be considered.

Applications of segmentation principle can be observed in thenew design of Jamaraat Bridge in Saudi Arabia. We will discuss thisexample further in the coming sections.

‘‘TRIZ Journal Website”).

OOvercrowded

Fig. 5A. Overcrowded exit and entry path.

Fig. 5B. Illustration of a tunnel within a house.

Table 4Some other principles that are applicable crowd management.

Principle Standard solution

Principle 23 Introduce feedback (referring back, cross-checking) toimprove a process or action

Feedback

Principle 33 Make objects interact with a given object of the samematerial (or material with identical properties)

Homogeneity

Principle 10 Perform, before it is needed, the required change of an object(either fully or partially)

Prior action

S.C. Pin et al. / Safety Science 49 (2011) 286–291 289

5.1.2. Principle 7: Nested dollAn idea generated from this principle is to have a building in-

side another building. If the overcrowding problem happens atthe exits of a busy building, an exit tunnel which is built beneaththe building might help (Figs. 5A and 5B). This is an effective meth-od to avoid overcrowding and crushing of people in the case ofemergency evacuations or even for normal yet overcrowded situa-tions. By applying this principle, more space is provided to thepedestrians and a subgroup of people will be directed into a lesscrowded area.

5.1.3. Principle 17: Another dimensionThis principle suggests us to think of changing the dimension of

the structure. Thus, the idea which comes to mind from this prin-ciple is to arrange the crowd into multiple floors (vertically) in-stead of a single floor (horizontally) as shown in Fig. 6.

This change of dimension allows the accommodation of morepeople without affecting the area occupied by the building. How-ever, the total area is increased as a result of the different structuredimension.

It is wise to review all the 40 principles other than those re-sulted from the contradiction table. Some unlisted principles mightalso help us to find possible solution to our problem. We thereforereviewed all of the 40 principles to figure out whether there arestill any other possible useful principles which might lead us tosolutions? We found that there are three more principles whichare applicable to crowd management problem. Table 4 lists thethree new principles we identified.

Fig. 6. Illustration of changing a building’s dimension.

5.1.4. Principle 23: FeedbackIt is desirable to be able to accommodate more people in a par-

ticular place but there is a limit to the safe density of the people inan area. If the margin value is exceeded, crowd disasters will prob-ably happen (Still, 2000). Thus, one of the measures is to monitorthe total number of people entering a place (or the average den-sity) and when the maximum value has reached, that is no morevisitors should be allowed to enter it. A sensor-enabled entry pointcan be used to detect and calculate the number of people going inand out. An alternative is to use computer vision technologies tomeasure the crowd density. The data received by sensors will besent to a computerized system (feedback). Once the maximum orcritical value of people or average density has reached, a warningalarm will inform the authorities to avoid more entries.

5.1.5. Principle 33: HomogeneityThis principle can be used in hybrid with Principles 1 (Segmen-

tation) that we discussed earlier. We may perform the segmenta-tion of crowd based on similarities like age, sex, purpose of entryand so on. It is believed that people with similar characteristic orcriteria will react almost the same in a crowd. Reacting in a similarway is very important in crowd management especially duringevacuation or emergency. For example, pedestrians with the sameage will run with almost the same speed. If people from differentages are mixed, older people for example will move slower and willslowdown others. However, this might not be practical in most ofthe situations. For instance, members of a family will prefer tomove with each other in a concert hall while in a stadium it mightbe possible to consider a separate section for senior citizens.

Another hybrid solution can be based on the travelling routes. Itis possible to divide a path and allow the crowd flow in just onedirection in each of the sections (Fig. 7).

The flow of pedestrians will be smoother after they are seg-mented into two mono-directional paths. Pedestrians will no long-er collide with those coming from the opposite direction.

5.1.6. Principle 10: Prior actionIt is important if we can educate the people on precautions to

take and also if there’s any unwanted incident, what do they needto do during emergencies. This education or knowledge should be

Fig. 7. Turning bi-directional flow to mono-directional flow.

A C

Elliptical Pillars

Multi-level

290 S.C. Pin et al. / Safety Science 49 (2011) 286–291

applied to both organizers and crowds. The organizers need tounderstand and possess the skills and knowledge to control thehuge number of crowds during emergency. This can be very disas-trous if they do not prepare well.

For the crowds, they need to learn the steps required whenemergency occurred so that they will not panic. In addition, theyshould know the way for them to trigger alarm if a potential prob-lem really occurs.

B

Fig. 9. New design of Jamaraat Bridge (‘‘Jamaraat Bridge in Makkah”).

5.2. Trends of Evolution

A trend of evolution is another useful technique in TRIZ. Trendsare used to predict the future characteristics of the products in theprocess of product evolution. This concept is based on the fact thatall products, processes or technical systems evolve over time. TRIZresearch has found that there are certain patterns of evolutionwhich repeats in every product or system.

Two patterns of evolution have been identified which might de-scribe the evolution of crowd management strategies.

Fig. 10. Crowd waiting at the single entrance.

5.2.1. Trend 1: Action coordinationThe flow of this trend is shown in Fig. 8.This trend has contributed to the idea of developing a crowd

density estimation system (CDES) (Yatim et al., 2009) that providesfeedback information to people and allows coordinating their ac-tions. Pedestrians in the crowd will be able to select better and lesscrowded paths and this will help to avoid more overcrowding insensitive areas.

The proposed crowd management system actually follows theevolution pattern. It starts from unmanaged crowds (non-coordi-nated action) to crowds managed using some barriers (partiallycoordinated action) and finally evolving into management withtechnology-assisted methods. For example, walkie–talkie mightbe used along with crowd monitoring and management software(coordinated action) and finally it may evolve into a system wherethe crowd can self-monitor their own situation and take prior ac-tion before any tragedy happens (action during interval). This pro-posed system is also generated from the idea of Principle 23(feedback).

5.2.2. Trend 2: Decreasing human involvement with increasingautomation

The application of the proposed system in crowd managementis a trend. It evolves from the involvement of security personnelto leveraging the technology to reduce workload. This shifted trendindicates the decreasing human involvement.

With such an automated crowd density estimation system, weminimize manual monitoring of the crowd density using nakedeyes.

Non-coordinated action

Partially coordinated action

Coordinated action

Action during interval

Fig. 8. Action coordination trend.

5.3. Related case studies

We have chosen two case studies to evaluate the principles de-scribed and also the effectiveness of the suggested solutions. Thetwo case studies are the new Jamaraat Bridge and the PhilSportsStadium.

5.3.1. Jamaraat BridgeThe first case study that we have investigated is the Jamaraat

Bridge in Saudi Arabia. Millions of Muslims visit the place duringstoning of the devil ritual of the Hajj. A lot of crowd related inci-dents happened there and the more serious one was on 12th Jan-uary 2006, nearly one million pilgrims gathered at the Jamaraat.Many security forces were assigned to control the crowd at theplace. Unfortunately a serious stampede occurred and caused hun-dreds of pilgrims to trample to death in a couple of minutes.

The old Jamaraat Bridge was rebuilt with a new design toaccommodate more people on the bridge, reduce overcrowding is-sues and hence increase the safety.

The most important feature of the new bridge its multi-level de-sign. The idea is to increase the capacity of pilgrims by adding mul-tiple floors. The bridge has a ground level, three additional floorson top of it and a deck. The five-floor structure (Fig. 9) can

Fig. 11. The flow of the crowd after entering the stadium.

Barrier

Zone A Zone B

Zone CZone D

Fig. 12. Illustration of a stadium with four entrances and segmented with barriers.

S.C. Pin et al. / Safety Science 49 (2011) 286–291 291

accommodate up to half a million pilgrims per hour, which meansit can now be used for three to five million visitors per day.

Although the TRIZ methodology was not the basis of the newdesign, we found that it is actually consistent with the TRIZ princi-ples. One of the TRIZ recommendations is to satisfy the contradic-tion between improving the crowd’s capacity and the relative areaby adding more dimensions (Principle 17). This principle suggeststhe use of multi-story arrangement instead of a single-story andthis is exactly what has been done in Jamaraat Bridge.

The second change that we have noticed is the division of thecrowd into different areas. The crowds will be led to different floorsby different ramps or paths according to their sources. For instance,the people coming from Suqul-Arab and Al-Joharah (eastern area)will get on the ramp that will take them directly to the first floorwhereas crowd from western area of Makkah can go directly tothe second floor. As shown in Fig. 12, paths A, B and C will guidethe crowd to different floors without interference with each other.

The idea of grouping the crowd into different floors is consistentwith segmentation principle (Principle 1) of TRIZ. The benefitsfrom segmentation have been discussed earlier in the paper. Theimmediate effect of the design changes has been to avoid any inci-dents in the following Hajj.

The third TRIZ principle that has been applied in JamaraatBridge is Principle 33, Homogeneity. This principle suggests thatonly elements with identical property should interact with eachother. The application of this principle can be observed in thechange of bi-directional crowd flows into a strictly one directionalflow. Movement of pedestrians in the same manner will reduce thechance of collision with each other.

5.3.2. StadiumStadium is an example of the places where crowd disasters

might happen. We have studied the PhilSports Stadium stampedein Pasig City, Metro Manila in the Philippines on February 4,2006. According to the BBC news (‘‘Manila stadium stampede kills73”), there were about 30,000 people gathered outside the stadiumparticipating in the first anniversary episode of the popular ABS-CBN television game show, Wowowee. The stampede started whenorganizers of the show prepared to hand out tickets to the crowdwith many of them had been camping outside the stadium for dayshoping to get the tickets. Some of the people were trying to getahead of the queue. Those outside the gates started pushing,prompting security guards to close the entrance gates. The situa-tion became worse and the gate finally collapsed. People in thefront of the crowd stumbled and fell. As a consequence, stampedehappened.

This incident caused the death of 71 people and 392 peoplewere injured. Investigation showed that the root cause of the inci-dent was the limited tickets available for a very large crowd, withmany of them had been waiting for days in order to gain entry tothe stadium. In addition, the entire crowd was gathered in one en-try point because there is only one entrance available for the sta-dium (Fig. 10).

Lack of multiple entries was the problem. People were trappedin the big crowd and became agitated. Furthermore, people neededto walk around the stadium to find their seat (Fig. 11).

The overcrowding can be reduced by segmenting the audienceinto 4 categories according to the seats. This is the idea from TRIZPrinciples 1 (Segmentation). Four entry points will be created in-stead of single one. Barriers can be built to segment the area intofour zones (Fig. 12). Each entry point will lead the audience intothe respective zone.

This idea is applicable to all stadiums. One example of such sta-diums is the Emirates Stadium which has four entrance doors. Nomajor crowd disaster has happened in Emirates Stadium until now.

6. Conclusions

TRIZ is a useful tool which helps in solving problems by elimi-nating contradictions. We applied TRIZ methodology to over-crowding problem and it provided us with useful insight andpotential solutions for our problem. The obtained solutions canbe further refined and possibly tested with simulations in orderto identify their feasibility. If the simulations prove the effective-ness of a potential solution, it might be incorporated into thecrowd system to increase the performance and safety.

Acknowledgements

We wish to thank Dr. Yeoh Teong San for his willingness to re-view our paper. This work is partially supported by e-science Grant(Ministry of Science, Technology & Innovation, Malaysia) and USMHajj Research 1428-1430H in collaboration with Umm Al-QuraUniversity, Makkah, Kingdom of Saudi Arabia (Ministry of HigherEducation).

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