MT5003 - Crowd Management System Report

MT5003 Creativity and Innovation

Report By:

Chua Teng Hou (HT073016M)

Hossam El Shenawy (HT072894R) Lim Ching Wu Leslie (HT063039Y) Nguyen Thanh Qui (HT073172B)

Hao Yun-Hsin (HT073093A) Shah Jehan (H073251H)

Shubha Agarwal (HT073167L) Tan Sung Chyn (HT062932E) Xu Nian Dan (HT063137U)

Ying Feng Wei (HT073194W)

MRT Crowd Management

System

Division of Technology and Engineering Management MT5003 Creativity and Innovation

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EXECUTIVE SUMMARY Innovation can be found in everyday life and creativity can be applied to solve that everyday

frustration. This project examined the problem of human congestion in transportation

networks and sought to propose a solution which not only attempts to regulate the issue but to

extract value from the problem posed.

One of the common frustrations arisen from the brainstorming and discussion sessions was

the problem of crowded MRT train carriages. As Singapore aims to increase the population

from 4.5 million to 6 million, the situation of crowding in the public transport will get worse.

The population is also aging. The movement of elderly is much slower and this increases the

likelihood of congestion. This project investigated on the value of providing information on

the occupancy a train carriage and exploiting this information to present value preposition to

different stakeholders.

Train operator and train commuters were identified as the two main stakeholders. Occupancy

is defined as the available of carriage space for commuters to stand and sit. It determined the

type of technologies to be used to capture the data. The integration of the proposed solution

into the existing infrastructure with minimum disruption and ease of installation was also

considered.

It was concluded that the weight of the carriage has a direct relationship to the number of

people inside. Unoccupied spaces consist of empty seats and standing spaces in the carriages.

As weight is the summation of the people within the carriage, it has the advantages of being

relatively accurate, and small data size (for the ease of processing). Through talking with the

commuters, precious feedback on the level of acceptance of such a service was received. The

feedback helped in deciding whom to market this solution and methods of distributing the

information. SMRT expressed great interest in the information obtained by the system. Users

welcomed the initiative. They believed that such information would be helpful to them when

they travel on the trains.

It is proposed that the effort should be focused on implementing the system for the potential

corporate customer, SMRT, and helping them to exploit this information to generate revenue.


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The occupancy information can be provided to all for free using the data display board. This

information on the movement of the crowd across the MRT network at different times can

also be capture. Trends on human traffic that are identified are useful to SMRT, and its

advertisers. For future expansion, it is also foreseen that additional market value can be

derived from the sale of information.


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CONTENTS

EXECUTIVE SUMMARY .................................................................................................................................. 1

BACKGROUND ................................................................................................................................................... 4

PROBLEM DEFINITION..................................................................................................................................... 6

MOTIVATION ...................................................................................................................................................... 6 PROBLEM IDENTIFICATION ................................................................................................................................. 6 PROBLEM VERIFICATION .................................................................................................................................... 6 PROPOSED SOLUTION OUTLINE .......................................................................................................................... 7

PROPOSED TECHICAL SOLUTION............................................................................................................... 8

OVERVIEW.......................................................................................................................................................... 8 SYSTEMATIC VIEW ............................................................................................................................................. 9 KEY PROCESSES ............................................................................................................................................... 10 SMS GRAPHICAL USER INTERFACE.................................................................................................................. 11 WEB ACCESS APPLICATION.............................................................................................................................. 12 ESTIMATED COST ............................................................................................................................................. 12 COUNTING NUMBER OF PEOPLE IN A TRAIN CARRIAGE.................................................................................... 12 ADVANTAGES OF WEIGHT AS MEASURING PARAMETER .................................................................................. 13 PROPOSED CARRIAGE SPACE SENSOR IMPLEMENTATION ................................................................................. 14 ADVANTAGES OF THE TECHNOLOGY ................................................................................................................ 15 DISADVANTAGES OF THE TECHNOLOGY ........................................................................................................... 15

MARKETING PLAN .......................................................................................................................................... 16

PRODUCT (MRT CROWD MANAGEMENT SYSTEM SOLUTION) ......................................................................... 16 MARKET IDENTIFICATION................................................................................................................................. 17

BUSINESS MODEL .......................................................................................................................................... 18

INFRASTRUCTURE............................................................................................................................................. 18 OFFERING ......................................................................................................................................................... 19 CUSTOMERS...................................................................................................................................................... 19 FINANCE ........................................................................................................................................................... 19

CONCLUSION ................................................................................................................................................... 20

REFERENCES.................................................................................................................................................R-1

APPENDIX A: ALTERNATIVE TECHNOLOGIES.....................................................................................A-1

APPENDIX B: CAPACITANCE MEASUREMENT EXPERIMENT ......................................................... B-1

APPENDIX C: PROBLEM VERIFICATION EXPERIMENT .....................................................................C-1


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BACKGROUND The frustrations of everyday life is a source of inspiration where if addressed can yield

unimaginable rewards. Products such as the staple, the papers clip or Post-it ™ notes are such

examples. There is value in rubbish if the value potion of it can be extracted commercially

and that give rise to the recycling industry that recovers scrape metals or precious metals

from discarded electronics. In the knowledge economy, the concept of value extends to

information. Information can be distributed at very little cost, high speed and wide spread

with the Internet. Channel marketing by Amazon, newsletters, Internet marketing are trends

that taking advantage of that concept of “value”. This project examined the truths in the

above three trends and seek to leverage on them.

After several discussions, it was agreed that human congestion is a common frustration and it

is often encountered in the MRT train.

Is there value in data on carriage occupancy rate? How can we extract such data in a simple

and effective ways? Is such a method scalable? If the initial idea proved to be commercial

variable, can it be applied to other parts of the world especially the developing countries

where the congestion is many times worse? Can the developed countries benefit from such

information as well? Logic dictates that if it is a common frustration, there should be some

value to all the affected users. These questions were asked during the discussions.

Demographic is changing and Singapore population is positioned to reach 6 million, the

critical mass defined to be essential to provide sufficient and healthy domestic demand to

support the economy. Aging is also a global trend. With a larger and aging population, human

traffic congestion will get more challenging. Increasing the capacity of each transportation

capability such as increasing the number of taxis, buses, trains frequency can only address

one facet of the issue. Optimizing the usage of the infrastructure is another aspect that is

harder to tackle due to the inclusion of the behavior of commuters. Inconsiderate commuters

may clutter at platform doors, occupying more seats to secure greater comfort at the expense

of other commuters. The team recognized that it is preposterous to try to dictate commuter’s

behaviors or human behavior as a whole. Similar to culture, behaviors develop over time.


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Due to various social disturbances or events, parts of them they are either weaken and

changed or reinforced and strengthen. In order to influence behavior, an effective technique

is to empower them with the ability to do the task (“Can I do it?”) and to provide the

motivation for them to do so (“Do I want to do it?”).

The team envisioned that by making the data on occupancy of carriages easily available to

the commuters; it will empower commuters to make a choice by seeking out a less crowded

carriage for greater comfort. In another words, the service will help the users to have more

control in getting a more comfortable ride. Additional market values can be created by

exploiting other forms of information derived from the carriage occupancy data.

The next few sections of the report cover the problem statement, the technical solution, and

the business aspects of this project.


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PROBLEM DEFINITION

Motivation

MRT is an important and major mode of transport for people in big cities such as Singapore.

It is an effective way to save energy, counter crowded traffic problems and reduce pollution

at the same time. Striding forward towards the next 20 years, mass public transportation in

cities will faced growing problems in both human congestion and stressed social behavior

due to the rapidly growing city population.

Problem Identification

An example of an unpleasant scenario is when a commuter chooses to board a carriage which

turns out to be crowded and is squeezed inside for a long time. During peak hours, picking

the wrong carriage will mean having to wait for the next train in order to board. Most of the

time, picking the right carriage depends on luck. The fundamental problem every train

commuter faces is being unable to find seats or adequate boarding space. The problem will be

exacerbated with train delays which will cause size of crowd to increase. Moreover, space

and tranquility will be at high premium be it at arm’s length or standing under your fellow

traveler’s armpit. Such unpleasant MRT experience may make people less willing to travel by

MRT. Commuters in Singapore and around the world need more information about the

availability of space in train carriages.

In the case of Mucha Line in Taipei and LRT in Shanghai where the carriages are separated

with no linked passage, a bad choice on a packed carriage would be irretrievable.

Problem Verification

An experiment was conducted to find out about the commuters distribution pattern in each of

the carriages of the train. Data was collected on the number of passengers in each carriage of

a train on the East-West SMRT line (Clementi Station to Bedok Station and back). It was

found that commuters were not equally distributed among the six carriages. Thus, there is a

value in providing the information about train carriage occupancy to ease the problem

identified. Results can be found in Appendix C.


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Proposed Solution Outline

The proposed solution is to design a system that collects the information on train carriage

occupancy and offers it to commuters, so as to equalize the number of passengers in each

carriage. However, this information may be less useful when the train is almost full.

Considerations were made to ensure that the proposed solution should be easy to implement

and cost effective as well.

Besides resolving the problem identified, the proposed solution will also serve multi facets of

mass train transit in providing the following:

• Load monitoring for mass transit operators

• Revenue generation for solution partners

The next section elaborates on the technical details of this proposed solution.


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PROPOSED TECHICAL SOLUTION

Overview This section presents the overview of the proposed technical solution. Figure 1 shows the

conceptual diagram of the subsystems in the MRT Crowd Management System.

Figure 1: MRT Crowd Management System Conceptual Diagram

It consists of three subsystems: the Density Collector, the Crowd Density Data Centre, and

the Density Information Distributor.

Train Central Data Applications

Crowd Density

Database

Density Collector

Density Data

Receiver Density

Information Distributor

Display Board

SMS


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1. Density Collector - The density collector is used to collect the data on the

occupancy information in trains. It consists of three components: the carriage space

sensors, data fusion box and the GSM modem as shown in Figure 2. The carriage

space sensors measure the weight of the carriages. The workings of the carriage space

sensors are explain in the later section. With proper calibrations, they determine the

crowd density. The data fusion box digitizes the data and formats it into a message to

be transmitted by the GSM Modem over the local telecom GSM network.

Figure 2: GSM Modem

2. Crowd Density Data Centre - The Crowd Density Data Centre consists of another

GSM modem that captures the data from all density collectors in every train and

stores the data in the central database. Real-time train carriages occupancy data is

used with other existing data such as schedule of trains to generate more value added

analysis.

3. Density Information Distributor - The Density Information Distributor consists

of the various applications that utilize the information generated by the Crowd

Density Data Centre.

Systematic View This section provides the systematic view of the MRT Crowd Management System. It

explains the architecture of the system in terms of key processes, and the flow of the

information from the collection of data to various applications. The processes are divided into

three major parts: Data Acquisition, Processing, and Dissemination.

Data Acquisition is the process of collecting and aggregation of data in the train. Processing

is the aggregation of data from every train to generate useful information. Dissemination is


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the distribution of generated information to the various applications and value-added services.

Figure 3 illustrates this systematic view.

Figure 3: MRT Crowd Management System Systematic View.

Key Processes The key processes in the MRT Crowd Management System occur at four different locations:

the Train, the Data Centre, the Train Station, and the Consumer.

On Trains:

1) Sensors are installed in individual carriages of each train to sense the available capacity of

each carriage as train leaves a station. Data from each sensor are digitized and sent to the data

fusion box

2) Consolidated data are formatted into a SMS message. This message consists of available

capacity of each carriage and next station where train will be approaching.

3) The SMS message is transmitted to the local mobile cell station, and routed to the mobile

cell station at the data centre.


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At Data Centre:

4) Data received at the data centre is stored in the central database and processed. The

information is published to the transport provider’s portal, and serves each station as web

services, via the Internet.

5) Phone operators at the data centre or any other location will be able to have real time

access information of available capacity in any train. They will be able to answer to queries

about capacity through the hotline

At Train Stations:

6) Information of the approaching train at each station is retrieved from the data centre

through the Internet. Ez-Link cards owners pre-register their mobile numbers with their cards.

As they tap their card into the stations, the latest information at respective stations are sent to

their mobile numbers

7) This information is also broadcasted via Wi-Fi to PDA owners who have installed the

software on their PDAs. This information can also be added to the display panels at the

platforms.

SMS Graphical User Interface

Fig xx show a possible screen for users who subscribe to the SMS service of the MRT Crowd Management System. The occupancy information will be displayed with the carriages with the most space shown on the first screen, and the remaining carriages shown in the second screen.

Figure 4: SMS Service Graphical User Interface.


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Web Access Application The web returns not only the coming trains’ information, but also allows the user to specify

their special queries. For example, a commuter living in Clementi wants to board a MRT in

10 minutes’ time, he/she probably wants to find out what is the MRT density level currently

between Boon Lay and Chinese Garden so that he/she can make an informed prediction.

Estimated Cost

Setup Cost:

1. Per Train Sensors: - $1000 Wiring - $500 ADC - $200 Data Fusion Box - $800 Software - $150

2. Data Centre Database Server - $4000 Application Server - $3000 Web Server - $2000 2 x Operating Systems - $1500 each Data Routing Software - $3000 2 x Physical Servers - $4000 each

3. Per Station Station Terminal - $800 Operating System - $1500 Data Routing Software - $400 Router - $200

Maintenance Cost: Per Train - $200 per month Data Centre - $10000 per month Per Station - $200 per month Counting Number of People in a Train Carriage The possibilities of measuring many related parameters were examined to find a way of

counting or estimating the number of people occupying a single MRT carriage. This section

discusses the working solution adopted and for completeness, Appendix A list the rest of the


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methods investigated. It was found that the weight of the carriage is the most appropriate and

directly related parameter to the number of people in each individual carriage for the reasons

stated in the following section.

Advantages of Weight as Measuring Parameter 1. It is an integrating property that is directly related to the occupied space in the

carriage. By measuring the weight at one strategically selected point in the carriage we get a

consolidated estimate of the number of people inside it. A heavy-weight passenger will weigh

more than the average-weight one but he/she still occupies more space than the other.

2. No computing power is needed. Unlike some of the other solutions we examined

that used a digital video or a still camera combined with a software algorithm to process the

captured images and detect the number of people (see Appendix A), this solution needs no

computing power and the weight reading is directly related to the number of people or the

space they occupy within the carriage. This reduces to a great deal the complexity of

implementing this solution.

3. No infringement on the privacy of the passengers. The issue of infringing on the

privacy of the passengers was always raised whenever we discussed other solutions that

required the use of a video or a still camera, either for further digital image processing or to

broadcast it directly to the passengers waiting on the platform of the next station to decide for

themselves which carriage to fit in (see Appendix A.)

4. Low cost. The components needed to implement this solution are low cost ones. Cost

analysis is discussed in the Financial Plan section of this report.

5. Proven to work well in similar situations. For a long time, weight has been the most

preferred measured physical property to assess the size of the payload of both moving and

stationary vehicles and rolling stock, however for other purposes than ours. On highways, the

payload of a traveling truck is measured in a weigh station to calculate the toll levied for

highway access by this truck. For the same purpose, railroad scales are used to weigh the

contents of train carriages (see Appendix A on Alternative Technologies for more details.)

Even the Westinghouse AC system used in the Singapore MRT trains makes use of weight


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measurement to step up the AC power in any MRT carriage whenever the number of

passengers in this carriage exceeds one hundred.

Proposed Carriage Space Sensor Implementation The solution propose the implementation of the carriage space sensor using Linear Variable

Differential Transformer (LVDT) displacement sensor or an Inline Load Cell which will be

mounted in the suspension system of the carriage to measure the weight or the vertical

displacement of the body of the carriage above its axle which is directly related to the weight.

LVDT are inductive displacement transducers that have proven themselves as very robust and

particularly suitable for use in installations where high vibrations, high accelerations and/or

very long cycle life are to be expected. Oscillations with small sweeps and measurements

smaller than 1mm can be achieved.

Figure 5: LVDT Sensors.

Typical LVDT sensors are energized with AC voltage,

produce an AC output and thereby require external

electronics for amplification and processing. However a

lot of companies do produce now LVDT sensors that

incorporate internal electronics allowing the transducer

to be supplied with either ±15VDC or 24VDC and

provide an output signal of 0 - 5V, 0 - 10V, 0 - 20mA

or 4-20mA. This feature allows for simple field

integration.

The output signal (voltage) from the LVDT sensor or the Load Cell placed beneath each

carriage will then be sent by wire to a central unit situated in any desired place on the moving

train. The measured voltage signals will then be translated into numbers by readily available

off the shelf indicators (which give a reading that is directly related to the level of occupancy

in the respective carriage) and transmitted via the mobile phone network to the control station.


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Figure 6: Inline Load Cell. Figure 7: Weight Indicators.

Advantages of the Technology 1. Load Cells are used in industrial applications of tonnage, simple, reliable and robust

(capable to measure 500 tons).

2. Literally measures a carriage to obtain the total weight of people in each car.

3. As with other sensors, can output an electric signal for data processing

Disadvantages of the Technology 1. Minor modifications of the rolling stock may be required to slot in the sensors.

2. Requires data maintenance – update of relationship between the people occupancy

and weight data obtained to factor in demographic trends (need not be done frequently).


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MARKETING PLAN Product (MRT Crowd Management System Solution) As a company, the MRT Crowd Management System is offered to the customers as the key

product. By implementing the system, customers will be able to measure, collect and manage

the crowd density while servicing their customers and this would eventually help them

increase the service efficiency and customer satisfaction.

The MRT Crowd Management System is designed to be a “total solution” which include the

hardware system, software system and multiple applications, these applications are for our

customers to increase the flexibility of implementing the system, depends on their existing

infrastructure and business model. As mentioned previously for our current customer –

SMRT, the applications are Display board and SMS, we suggest SMRT launch a two-phase

service offering, in the first phase displaying the message on LCD board to the public for free,

this would help to expand the user base within a short period; in the second phase, SMRT can

align with Singtel to offer the SMS service to the mobile subscribers, this would add on a

new revenue stream to both SMRT and Singtel by charging their customer subscribing the

service. The product roadmap will also include:

• Combine SMS with Bluetooth technology to assure a more accurate service

provision.

• Provide Always-on newsletter as a real-time message on cell phone screen.

• Integrate the service interface into the 3G/4G mobile communication platform

in order to offer the end-user more flexible and customized service.

By keep innovating on product/service offering, better value proposition will be offered to

customers by enabling them to serve their customers better; meanwhile, first-comer

competitive advantage will be sustained by blocking the potential competitor from offering

the same product.


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Market Identification There is not yet any MRT crowd management system being deployed. Thus, the market for

such product is considerable. The domestic customer – SMRT, has agreed to field test our

design in its MRT system, aiming to obtain the real-time first hand crowd density information

in order to maximize the usage of carriage space and provide better and more efficient service

to public. There are plans for expansion to present international market such as China and

India after successfully entrenching the company as a leader in domestic market. In highly-

populated city like Shanghai and New Deli, such MRT crowd management solution will be

accepted by local public transportation company. In order to win the international accounts, a

mutual-benefit relationship with local partners will be fostered by providing them the

technical consultancy, financial support or the Intellectual property when they go to pitch

their local customers.


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BUSINESS MODEL A business model is a conceptual tool that contains a set of elements and their relationships

and allows expressing the business logic of a specific firm. Our business model contains three

main elements: Infrastructure, offering and customers. Following is a description of the value

we can offer to our customers by leveraging our technical innovation and engineering

infrastructure.

VALUEPROPOSITION

COSTSTRUCTURE

CUSTOMERRELATIONSHIP

TARGETCUSTOMER

DISTRIBUTIONCHANNEL

VALUECONFIGURATION

CORECAPABILITIES

PARTNERNETWORK

REVENUESTREAMS

Crowd management system is for customer to

increase service efficiency, customer satisfaction, and

revenue stream.

Key alliance with Singtel and Web2.0 SP

• Domestic accounts will be covered by direct

sales force.• International customers

will be served through our local partners.

Provide the total solution by integrating the internal designed platform with external

flexible application

Domestic customer SMRT has agreed to launch a prototype

field-trial test.

• COGS• Patent charge• Depreciation• Tax

• Product revenue• Service revenue

(sharing)

Domestic and international public

transportation company

• Technical expertise• Engineering capability• Intellectual property

INFRASTRUCTURE CUSTOMER

OFFER

FINANCE

Crowd Management System – Business Model

Figure 8: Business Model.

Infrastructure The core capability of the infrastructure is the technical and engineering expertise which

would keep developing innovative solutions for our customers. In order to sustain

competitive advantage, the design will be patented as Intellectual property for exclusive use.

In terms of supply chain, there will be fostering of partnership with key supplier to optimize

supply efficiency and cost structure. Partner network also include the key alliance with

telecom company like Singtel and web-based service provider such as Yahoo or MSN, the


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value configuration is to provide customer the “total solution” by integrating the internal

design and innovation with external infrastructure and capability so as to increase the

flexibility implementing the managing the system.

Offering As mentioned earlier, the value proposition offered to the customer is to help them increase

the service efficiency, customer satisfaction, and revenue stream.

Customers The target customer of the business is the domestic and international public transportation

company. Direct sales force will be used to cover the domestic accounts such as SMRT, and

local partners like engineering consulting company will be recruited to cover international

customer, so as to better serve them.

Finance The cost structure of the business generally includes four parts, specifically they are COGS

(Cost of goods sold), patent charge (expenses of filing a utility patent in USPTO),

depreciation and tax. The revenue on the other hand, mainly focuses on two streams of

income: first is the revenue of the product sold, second is by sharing the income of SMS, web

service being subscribed.


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CONCLUSION

By defining a problem which is faced by us on a regular basis using brainstorming techniques,

talking to potential customers and conducting experiments to verify problems, we have

exploited existing technologies to devise a solution which will not only benefit the general

public but also our potential customers in managing the crowd by means of available

information that this system intends to provide.

The few important benefits of this system, such as its non-invasive, the safe and easy

implementation, the easy maintenance, and the cost effectiveness make it even more viable

and effective. Overall this system serves a social cause and has a monetary potential to be

extracted which is ultimately the main goal behind any innovation.


R-1

REFERENCES

[1] L.Y. Tan, First Mrt Accident, Singapore Infopedia, 2004. http://infopedia.nlb.gov.sg/articles/SIP_814_2004-12-31.html Retrieved on 19 Sep 2007.

[2] Siemens C651 Car, Wikipedia, 2007. http://en.wikipedia.org/wiki/Siemens_C651_Car Retrieved on 19 Sep 2007.

[3] P.D. Rockwell, Measuring Power Transmission Loads Directly, Plant Services.com, 2007. http://www.plantservices.com/articles/2006/076.html Retrieved on 19 Sep 2007.

[4] Load Cells, Electronic Information Online, 5 Nov 2006. http://www.electronics-manufacturers.com/info/data-acquisition/load-cell.html Retrieved on 20 Sep 2007.

[5] Multi-Car Loading Station, Free Patent Online, 2007. http://www.freepatentsonline.com/4284380.html Retrieved on 20 Sep 2007.

[6] Direct Industry, 2007. http://www.directindustry.com/ Retrieved on 26 Sep 2007.

[7] K. Kudo, K. Mizutani, T. Akagami and R. Murayama, Temperature Distribution in a Rectangular Space Measured by a Small Number of Transducers and Reconstructed from Reflected Sounds, Graduate School of Systems and Information Engineering, University of TSUKUBA, 10 Feb 2003. http://jjap.ipap.jp/link?JJAP/42/3189/ Retrieved on 26 Sep 2007.

[8] K. Mizutani, Acoustic Method for Measuring Room Temperature Distribution, Takenaka Co., 10 Jan 2001. http://www.takenaka.co.jp/takenaka_e/news_e/pr0101/m0101_01.htm Retrieved on 26 Sep 2007.


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[9] How Infrared motion detector components work, GloLab, 2007. http://www.glolab.com/pirparts/infrared.html Retrieved on 29 Sep 2007.

[10] Pyroelectric Sensor, Eco-Sensor, 2007. http://www.eco-compteur.com/Pyroelectric-Sensor.html?wpid=15533 Retrieved on 1 Oct 2007.

[11] Passive Infrared Sensor, Wikipedia, 2007. http://en.wikipedia.org/wiki/Passive_infrared_sensor Retrieved on 1 Oct 2007.

[12] References Mass Transit Vehicle, Siemens, 2007. http://references.transportation.siemens.com/refdb/showReference.do?r=455&div=5&l=en Retrieved on 2 Oct 2007. [13] Railway Track Design, The American Railway Engineering and Maintenance-of-Way Association, 2003. http://www.arema.org/eseries/scriptcontent/custom/e_arema/Practical_Guide/PGChapter6.pdf Retrieved on 2 Oct 2007.

[14] Track Design Handbook for Light Rail Transit, Transportation Research Board, 3 Sep 2000. http://www.trb.org/news/blurb_detail.asp?id=2561 Retrieved on 2 Oct 2007.


A-1

Appendix A: Alternative Technologies

The Linear Variable Differential Transformer (LVDT)

The Linear Variable Differential Transformer (LVDT) is a displacement measuring

instrument and is not a strain-based sensor. The LVDT models closely the ideal Zeroth-order

displacement sensor structure at low frequency, where the output is a direct and linear

function of the unit.

Figure A-1: LVDT.

The LVDT is a variable-reluctance device, where a primary center coil establishes a magnetic

flux that is coupled through a mobile armature to a symmetrically-wound secondary coil on

either side of the primary.

Two components comprise the LVDT: the mobile armature and the outer transformer

windings. The secondary coils are series-opposed; wound in series but in opposite directions.

Figure A-2: Secondary Coils.

When the moving armature is centered between the two series-opposed secondary, equal

magnetic flux couples into both secondary and the voltage induced in one half of the


A-1

secondary winding is balanced and 180 degrees out-of-phase with, the voltage induced in the

other half of the secondary winding.

The balanced condition provides total cancellation of secondary voltages and therefore zeros

voltage output. When the moveable armature is displaced from the balanced condition, more

magnetic flux will couple into one half of the secondary than into the other producing an

imbalance voltage output at the primary coil excitation frequency. The output voltage of the

LVDT is therefore a direct function of the displacement of the mobile magnetic armature.

The LVDT is, by definition, a transformer and requires an oscillating primary coil input.

The DC LVDT is provided with onboard oscillator, carrier amplifier, and demodulator

circuitry. The AC LVDT requires these components externally. Due to the presence of

internal circuitry, the DC LVDT is temperature limited operating from typically -40 C to

+120 C.

The AC LVDT is able to tolerate the extreme variations in operating temperature that the

internal circuitry of the DC LVDT could not tolerate. Typically, LVDT’s will be excited by a

primary carrier voltage oscillating at between 50 hertz and 25 Kilohertz with 2.5 Kilohertz as

a nominal value. The carrier frequency is generally selected to be at least 10 times greater

than the highest expected frequency of the core motion.

The external housing of the LVDT is fabricated of material having a high-magnetic

permeability therefore desensitizing the device from the effects of external magnetic fields.

No sensing spring element exists within an LVDT and therefore, the output of the sensor is

hysteresis-free. Some LVDT displacement measuring sensors are, however, provided with

internal armature return springs to allow profile measurement. When there exists no direct

contact with the moving armature is allowed no mechanical wear results. The provision of

linear bearings to prevent armature to coil structure contact and to limit wear can greatly

extend LVDT operating life expectancies.

The strong relationship between core position and output voltage yields a sensor design that

shows excellent resolution, limited more by the associated circuitry than the sensing method.


A-3

The internal core of the LVDT is generally constructed of an annealed nickel iron alloy with

the high-temperature limitations of the device limited to the curie point of the core and the

winding insulations used.

The thermal response characteristics of the LVDT are excellent for static and quasi-static

thermal environments due to the physical and electrical symmetry of these devices. The

physical symmetry also contributes to excellent zero repeatability over time and temperature.

Most thermal-sensitivity shift errors result from the significant thermal coefficient of

resistance (TCR) of the copper transformer windings. With increasing temperature, the

primary coil resistance will increase causing a decrease of the primary current in the constant-

voltage-excited case and therefore decreasing the magnetic flux generated and voltage output

correspondingly.

The use of constant-current excitation will ensure a constant primary flux regardless of the

coil resistance. Since the equivalent circuit of the constant-current source is a voltage source

with an infinite series resistance, the use of a low-TCR resistance, in series with the primary,

will function in much the same manner as the piezoresistive span-compensation resistor by

causing the primary voltage to increase as a function of temperature thus offsetting the TCR-

induced losses. The use of the series low-TCR resistor in the primary circuit allows the

constant-voltage source to appear to the LVDT as a constant-current source.

Other thermally-active methods may also be used to compensate for the primary winding

TCR by causing the primary voltage to increase, with rising temperature, in proportion to the

increase in the primary coil resistance. The temperature coefficient of magnetic permeability

is another contributor to the thermal-sensitivity shift and is compensated out as a net effect by

the means described above. Within approximately 2 seconds of power application the LVDT

oscillator and demodulator circuitry will stabilize sufficiently for dynamic measurement.

Due to self-heating of the primary coil, warm-up times for high precision static measurement

are comparable to strain gauge sensors and are dependent upon the thermal stability of the

measuring environment.


A-4

Low Profile Railway Scale This scale measures the weight of individual carriages of a train while in motion. It can thus

be installed after the end of the platform of every station to weigh the carriages of the train

just departing the station. The low-profile scale adapts to (or will be custom-made for) any

combination of car lengths.

Because it is mounted above ground in a shallow, concrete foundation, there is no worry

about shifting ballast resulting in weight errors. As a result, maintenance is minimized and

precious track time is rarely interrupted. That translates into money saved.

Various types of weight displays and printers are available to attach to this railroad scale.

They include: simple or complex electronic weight displays and printers, scoreboard readouts,

traffic controls and other custom weighing systems.

Other benefits of this solution are that installation is rapid and simple, allowing to get back on

track fast. Installation can be handled locally and usually requires only about two days.

Figure A-3: Low Profile Rail Scale.


B-1

Appendix B: Capacitance Measurement Experiment

Introduction The experiment to verify the feasibility of the capacitance measurement method was

scheduled on Saturday 20th October. The venue was Kent Vale Bus parking. One bus was

used to conduct the experiment.

Purpose The main purpose is to find a simple yet effective way to measure/estimate the amount of

people in a crowd. Specifically, in the context of this project, we aimed to provide solution

applicable for MRT transportation. A bus was used as resembles of a train carriage.

Experiment Three bands of aluminum tape was pasted along the ceiling of the bus and connected to

resemble one electrode of a capacitor. The other electrode was formed by another band of

aluminum on the floor. Capacitance will be measured between the top and the ground of the

bus and analyzed corresponding to number of passengers on ride. Following are some photos

taken during process:

Figure B-1: Top Electrode. Figure B-2: Capacitance Measurement Device.


B-2

Figure B-3: Queuing for the ride. Figure B-4: All boarded the bus. Results The readings were not following any logic manner and fluctuating, varying a lot. It was

significantly affected by temperature and air flow as when the door opens, people board or

alight, as well as the function of air-condition system. The action of grabbing the hand rail

also produced lots of variation, and there was no control over that factor. After discussion, it

was concluded that this method is too difficult to be made into an easy attach-and-measure

system which is of requirement.


C-1

Appendix C: Problem Verification Experiment

Introduction The experiment was conducted on SMRT East-West line stations from Clementi to Bedok on

3 November 2007, 1 to 2 pm. Figure C-1 shows the stations in the East-West line where the

experiment was conducted.

Figure C-1: Map of MRT stations where experiment was conducted.

Purpose The purpose of the experiment was to verify if the load (passengers) on the train was evenly

spread and if the boarding and alighting pattern of commuters was predictable or erratic.


C-2

Experiment Two people were located on each of the 4 carriages to count the passengers in the train after

the train doors closed, and the number of commuters that alighted and boarded the train at

each station

Results Part 1: SMRT train travelling from East (Clementi) to West (Bedok)

Graph C-1: Traveling West to East load on board of SMRT carriage.

The observations on this West towards East flow were:

• Heavy load towards city central interchanges of NEL-(Outram) and NS-(City

Hall).

• Normal to low load when train goes outwards beyond city central zone.

• Abnormally high load on board the 6th (last) carriage from Clementi to Outram

station.

• Travelers at the door openings of the 6th carriage were not able to board or

have difficulty boarding from Clementi to Tiong Bahru station.

West to East : Load on board of carriage

02040

6080

100120140

160180200

Cle

men

ti

Dov

er

Buon

a Vi

sta

Com

mon

wea

lth

Que

enst

own

Reh

ill

Tion

g Ba

hru

Out

ram

Par

k

Tanj

ong

Paga

r

Raf

fles

Plac

e

City

Hal

l

Bugi

s

Lave

nder

Kalla

ng

Alju

nied

Paya

Leb

ar

Euno

s

Kem

bang

an

Bedo

k

EW Station

No

of C

omm

unte

rs

1346

NELAbnormal very high load at 6th

NS

Possible (13x4=52) Available Seats

West to East : Load on board of carriage

02040

6080

100120140

160180200

Cle

men

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hru

Out

ram

Par

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r

Raf

fles

Plac

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City

Hal

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Bugi

s

Lave

nder

Kalla

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Paya

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bang

an

Bedo

k

EW Station

No

of C

omm

unte

rs

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NELAbnormal very high load at 6th

NS



C-3

The common assumption misunderstood by public is that the carriages are most likely

to be packed at the middle carriages of 3rd and 4th out of 6 carriages. Conclusion from

Part I of experiment shows that crowd density is not evenly spread as commonly

assumed. With the 6th carriage at almost maximum load capacity, a lot of travelers

standing at the door openings of the 6th carriage were dismayed to find it inaccessible

from Clementi to Tiong Bahru station. They would be found running towards 5th or

even 4th carriage to board the train.

Part 2: SMRT train travelling from West (Bedok) to East (Clementi)

Graph C-2: Traveling West to East load on board of SMRT carriage.

The observations on this East towards West flow were:

• Increasing load towards city central interchanges of NS-(City Hall) and NEL-

(Outram Park).

• Normal to low load when train goes outwards beyond city central zone.

• 1st carriage experience relatively high & similar load with 3rd and 4th carriages.

• “Expected” relative low load on board the first & last carriage.

East to West : Load on board of carriage

020

406080

100

120140160

180200

Bedo

k

Kem

bang

an

Euno

s

Paya

Leb

ar

Alju

nied

Kalla

ng

Lave

nder

Bugi

s

City

Hal

l

Raf

fles

Plac

e

Tanj

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Paga

r

Out

ram

Par

k

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g Ba

hru

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EW Station

No

of C

omm

unte

rs

1346


NEL

NS

East to West : Load on board of carriage

020

406080

100

120140160

180200

Bedo

k

Kem

bang

an

Euno

s

Paya

Leb

ar

Alju

nied

Kalla

ng

Lave

nder

Bugi

s

City

Hal

l

Raf

fles

Plac

e

Tanj

ong

Paga

r

Out

ram

Par

k

Tion

g Ba

hru

Reh

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own

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wea

lth

Buon

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sta

Dov

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Cle

men

ti

EW Station

No

of C

omm

unte

rs

1346


NEL

NS


C-4

From this experiment, it can be concluded that,

• Crowd density on each train carriage does not fluctuate abruptly with progressive

stations except in the case of Line interchanges and popular public destination like

Bugis.

• The 1st and last train carriage does not guarantee a lower crowded density relative

to the mid carriages.

These show that information disseminated to consumers will be useful to even out the load

distribution.

MT5003 - Crowd Management System Report

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