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Term Project Report, Fall 2012 MIE440F: Mechanical Design Theory and Methodology

Dept. of Mechanical/Industrial Engineering, University of Toronto

REDUCING UNEVEN PASSENGER DENSITY ON TTC SUBWAY PLATFORMS

Sissi (Haiyun) Wang (33%) Jennifer Wong (33%)

Song Yang (33%)

ABSTRACT

We describe the design process, as well as the final outcome, for the development of a product which promotes even passenger density on Toronto Transit Commission (TTC) subway platforms. We identify lead users and their needs in order to gain a greater understanding of the problem. We review competitive products, identifying their shortcoming, as well as their benefits. We then generate possible designs using a variety of methods, including 6-3-5, TRIZ, SCAMPER, and biomimetic design. Finally, we evaluate our concepts using both a weighted decision matrix, as well as a PUGH chart, to arrive at the final solution. The solution we propose consists of a series of barriers along the platform, which will visually segment the platform into sections. We believe that this will aid passengers in identifying less crowded sections, thereby promoting movement to those areas. The barriers are designed to have adjustable length, and can be easily installed without altering existing TTC infrastructure.

INTRODUCTION Overcrowding reduces the efficiency of transit systems in many countries. Although crowding itself is difficult to address without changing existing policy and infrastructure, some of its negative effects can be mitigated using product solutions. One such effect is the uneven distribution of passengers on loading platforms. Jaiswal et al. (2008) demonstrated a tendency for passengers to congregate in preferred areas of loading platforms when waiting for public transit. Moreover, these regions tend to be near platform entrances and exits. The most direct impact of uneven crowd density is an increase in train boarding times. Fang et al. (2003) showed an inverse exponential relationship between crowd density and crowd movement velocity. An increase in train boarding time results in less trains being able to service a station during any given time period, and further aggravates the crowding. Figure 1

shows the relationship between crowd density and walking velocity.

Fig. 1: Graph from Fang et al. (2003) showing the

relationship between crowd density and walking velocity. Note that this relationship holds even during emergency

situations. Overcrowding can also cause negative psychological, health, and financial effects. Psychological effects include higher stress levels, more aggressive behavior, and lower cognitive performance due to sensory overload (Sammons). Negative health effects include an increase in blood pressure and a depressed immune system (Sammons). Overcrowded conditions also facilitate the spread of infectious diseases. A major safety issue caused by crowding is possible injury and the loss of life if one were to get pushed off the platform.

From a financial standpoint, it is beneficial to solve platform crowding as getting one or more additional trains into the subway station within an hours time can buy an extra 3- 5%

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capacity and possibly an increase in ridership according to Adam Giambrone, the TTC chairman. According to New Yorks subway transit system, a 2% increase in ridership led to 1.3% increase in revenue in year 2012. It also saves passengers commute time allowing them to make more productive use of their time.

LEAD USERS

The lead users for the subway platform crowding problem are interpreted as people and professionals that have to deal with very large crowds on a regular basis, and who encounter crowds more frequently than the general population.

Who The lead users identified are: law enforcement, military, and daily TTC commuters. Law enforcement and military have to manage large crowds in chaotic situations such as riots through extreme measures of crowd control. Daily TTC commuters encounter the subway crowding problem more often than non-regular riders.

How A focus group was conducted to identify the daily TTC commuters needs. Six students from different disciplines at the University of Toronto were gathered to answer a series of questions with regard to their TTC commuting experience. The commuters came from various stations, each of which served a different purpose (e.g. interchange station, terminal station). The project group first set out to verify whether a crowding issue exists around subway platform staircases, and the commuters verified that crowding was an issue during high-traffic times. They then proceeded to identify the obstacles commuters faced that prevented them from dispersing themselves on the subway platform such as laziness, ineffective TTC signs and broadcasts, and following the crowd due to unfamiliarity with station. Finally, they asked improvement questions on how to improve the commuters TTC experience in order to extract the needs of the commuters to work into the product solution for reducing crowding.

What

The focus group participants provided suggested improvements that revealed underlying needs. Although the ideas proposed were improvements in infrastructure, we were able to extract from these three basic user needs: effectiveness, comfort, and accessibility. Table 1 categorizes all suggested improvements from the focus group participants into the three basic user needs.

Table 1: Identified user needs

Identified needs Participant responses 1. Effectiveness Conveyor belts, board trains faster 2. Comfort More benches, leaning against

walls, more personal space 3. Accessibility Wider platform, bigger doors, more

frequent trains, more staircases, better control of entrance vs. exit flow, open path across platform

Effectiveness is measured by the time it takes for passengers

to board the train. We assume that a more even distribution of passengers on the platform leads to a reduction in boarding time;

Comfort was measured by the amount of sensory discomfort a commuter experiences (e.g. standing instead of sitting while waiting); and

Accessibility is measured by the amount of clearance available for the commuter to travel from one point to another on the platform.

COMPETITIVE ASSESSMENT Our assessment of competitive products covered solutions currently employed by the TTC, as well as equipment used by the military and law enforcement in riot control.

Physical Barriers They can be seen at Bloor & Yonge station during high traffic times. They are effective at controlling the crowd movement, but have poor accessibility, making it difficult for people to travel from one point to another on the subway platform. Figure 2 shows the configuration of physical barriers at Bloor & Yonge station during rush hour.

Fig. 2: Barriers at Bloor & Yonge

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Signage & PA Broadcasts Signage and PA broadcasts are currently used at TTC subway stations to instruct passengers to spread out on the platform. However, they are not effective since they are a very passive method to direct crowds.

Law Enforcement Equipment An example of such equipment are the Mosquito alarm which emits sound at a very high frequency to disperse crowd and the Active Denial System which shoots focused electro-magnetic wave energy to disperse crowd. While they are effective at controlling the crowd, they are very harmful, cause discomfort for people, and are illegal for public use. Figure 3 describes what each component of the Active Denial System does during implementation. Table 2 provides a summary of the benefits and shortcomings of existing solutions.

Fig. 3: Conceptual diagram for the Active Denial System, which uses directed heat to disperse crowds

Table 2: Summary of the pros and cons of existing solutions

Existing solution Gap

1.Physical barrier Effective crowd control, but severe reduction in accessibility

2. Signage and announcements

Passive solution, ineffective

3. Law enforcement equipment

Effective crowd control, but harmful and illegal in public

CONCEPT GENERATION

Biomimetic Design Two concepts were generated using biomimetic design:

1. Using the word open, we found the following excerpt: The Na+ concentration is much higher outside the axon than inside, so when the sodium channels open, Na+ ions from the outside rush into the axon. This led to the One-way Turnstile, as shown in Figure 4:

Fig. 4: One-Way Turnstile turnstiles are installed halfway

between the platform entrance and platform end. Passengers are permitted to move freely from the entrance towards the end, but movement in the reverse direction is

limited.

2. Using spread, we found the following excerpt: Plant viruses may infect cells... then spread rapidly through... microscopic channels which traverse the cell walls of plant cells. This led to the Discretized Platform, as shown in Figure 5:

Fig. 5: Discretized Platform the platform is divided into several distinct segments using barriers. Passengers can

more easily identify crowded areas, and avoid them accordingly. Each segment is thought of as a cell, and the

open walkway on the platform is the channel.

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TRIZ We found it difficult to identify appropriate improvement and conflicting parameters. Therefore, we browsed through the list of TRIZ principles, and were inspired by No. 15 the Principle of Dynamism: Divide an object into parts capable of movement relative to each other. Using this, we developed the Seesaw Platform, as shown in Figure 6:

Fig. 6: Seesaw Platform several large plates of metal are installed onto the platform. Each plate is balanced on a fulcrum located in the center. The plate tilts when one

side has more passengers, resulting in a feeling of discomfort due to lack of balance. This motivates

passengers to relocate to the other side of the plate

SCAMPER In using SCAMPER, we selected as our base case the signs being used by the TTC. For S (substitute), we substituted the sense of vision with other senses, such as tactile or aural. From this we developed ideas such as PA broadcasts, also currently in use by the TTC, and placing heating units at the ends of the platform during the winter to encourage movement away from the center.

However, we felt these solutions were ineffective. By using M (magnify), we intensified them into a group of products we call Aggressive Solutions. These solutions aim to move users away from platform entrances through negative reinforcement. Figure 7 shows an example of an aural aggressive solution:

Fig. 7: An example of what an aggressive solution might look like.

6-3-5 The most interesting solution which resulted from our 6-3-5 brainstorming session was the Textured Floor, as shown in Figure 8:

Fig. 8: Textured Floor a rubber floor mat with protruding rubber spikes is rolled out at platform entrances/exits. This

discourages passengers from staying near staircases

CONCEPT EVALUATION/SELECTION

Seven criteria were used to evaluate the concepts. Three of these (accessibility, comfort, effectiveness) resulted from the focus group we conducted with frequent TTC commuters. The rest were factors identified during team discussions. The criteria were:

Accessibility: the amount of clearance available on the

platform (m2). This determines how easily a passenger can move from one location on the platform to another;

Adaptability: the number of stations at which the product can be deployed without being remanufactured with different specifications (e.g. size);

Comfort: the amount of sensory discomfort a commuter experiences while waiting;

Cost: the amount of money ($) required to manufacture the product, as well as the raw material cost;

Effectiveness: the time it takes for all passengers to board the train (seconds). We assume that increased evenness in platform density leads to reduced boarding time;

Durability: the amount of time before the product is expected to require repair (weeks).

We evaluated our design concepts using two methods: the weighted decision matrix and the PUGH chart. For the weighted decision matrix, we first evaluated the relative importance of our criteria using pairwise comparison:

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Table 3: Evaluation of criteria using pairwise comparison

Criteria A B C D E F G Weights

A) Accessibility - 0 1 0 1 0 0 10% B) Effectiveness 1 - 1 0 1 1 0 19% C) Comfort 0 0 - 0 1 1 0 10% D) Cost 1 1 1 - 1 1 0 24% E) Durability 0 0 0 0 - 1 0 5% F) Adaptability 1 0 0 0 0 - 0 5% G) Safety 1 1 1 1 1 1 - 29%

Total 100% We subsequently applied this to a weighted decision matrix, the result of which is found in Appendix A. Furthermore, we also used a PUGH chart to evaluate our concepts. The datum used for the PUGH chart was signs and PA broadcasts as currently employed by the TTC. The results of the evaluation are summarized below:

Table 4: Summary of results obtained using weighted decision matrix and PUGH chart

Concept Weighted Matrix PUGH Chart

Textured floor 2.10 -2 Aggressive solutions 1.62 -2 See-saw platform 1.38 -3 Turnstiles 1.86 1 Discretized platform 2.38 0

An interesting observation from the PUGH chart is that the majority of our concepts seem to perform worse than the TTC signage/PA broadcasts. This is due to the lack of weighted criteria in the PUGH chart. Because the current solutions employed by the TTC naturally score very high in accessibility (signs and broadcasts do not occupy platform space), comfort (signs and broadcasts do not directly impact passengers), and cost (signs and broadcast are likely less expensive than new products). Furthermore, due to the nature of our design concepts, the TTC solution also performs well in safety. The full PUGH chart, as well as the full weighted decision matrix, can be found in Appendix A: Concept Evaluation. Based on the results of the weighted decision matrix and PUGH chart, we selected the Discretized Platform as the final design concept. This result seems reasonable, since the discretized platform is the safest design out of all concepts. The aggressive solutions and seesaw platform pose obvious hazards to the passenger's safety. The textured floor poses a safety risk if

passengers fall, especially during winter, and the turnstiles are an obstacle in an emergency evacuation.

FINAL DESIGN

Focus was placed on designing the barriers which would be used to separate the platform into sections. Through discussion, we arrived at three constraints for the barrier:

The length of the barrier must be adjustable, since platform

width is not uniform across all TTC stations. Variable length would allow barriers to be deployed at multiple stations without remanufacture.

The barrier should be easy to install without modifying existing TTC infrastructure. The installation must be very secure, as people tend to lean on barriers (an affordance). It should also be easy to take down for maintenance.

The barrier must not lead to significant visual obstruction on platforms. This is a safety consideration.

Overall Structure

The final design is a barrier comprised of 4 panels nested within each other, with the innermost panel being solid. The innermost panel can be extended from second innermost panel, and the second innermost panel can be extended from the second outermost panel, etc., allowing for adjustable barrier length. The height of the barrier is 1m, and each panel has a length of 0.75m, giving the fully extended barrier a total length of 3m.

Fig. 9: Arrows depict the location of barriers relative to

train doors The number of barriers installed along a platform is chosen to be 5 since each subway train is comprised of 6 cars linked together. Each car has a set of doors at either end, allowing adequate space for the barriers to fall in between the doors, despite how the final locations of the train doors tend to be inconsistent on the platform. Figure 9 shows the relative locations of the barriers to the train doors. Considering safety aspects, the barrier was designed to minimize visual obstruction, therefore, a translucent plastic material is used for the main body of the panels. Each panel will have a surrounding frame with holes to secure panels with respect to each other. Figure 10 shows a possible configuration of the barrier with the innermost panel extended.

! ! ! ! ! ! ! ! !

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Fig. 10: Barrier with one panel extended In order to secure the barrier onto the platform, we propose to fix it in place at both ends. A vice will be used to clamp the barrier onto the edge of the platform, taking advantage of the existing overhang (see Figure 11).

Fig. 11: Cross-section of a TTC platform. Note the overhang at the edge of the platform.

The other end of the barrier will be secured onto the platform floor using a vacuum lock. When secured in place, the suction cup creates a strong vacuum, making it difficult to move the barrier. Figure 12 shows a vacuum lock when secured:

Fig. 12: An example of a vacuum lock

An additional challenge is securing the panels with respect to each other so passengers cannot modify the barrier length. We achieve this by placing holes in each panel, allowing them to be secured with Torx screws once in the desired configuration. Figure 13 shows the Torx security screw head pattern.

Fig. 13: Torx security screw head. We assume that the typical TTC passenger would not be in possession of a

screwdriver capable of removing such screws.

Material: The main body of each plate is made of Lexan, a brand of polycarbonate resin thermoplastic. Lexan is a resistant material, with a tensile strength of 60-70 MPa (Sabic 2008). Each plate is surrounded by an aluminum frame, which further improves the structural integrity of the barrier.

Table 4: Volume, weight, and cost for one barrier, broken down by material type

Volume (cm3) Weight (kg) Cost (US$)

Lexan 42750 51.3 $99.32 Aluminum 4709 12.71 $24.61 Total 47459 64.01 $123.93

DISCUSSION

Limitations of methods In terms of concept generation, we (surprisingly) found that biomimetic design generated the most interesting concepts. The greatest difficulty came in finding the correct keywords to use. Furthermore, our source was limited to one natural-language text. On the other hand, TRIZ was particularly difficult to use, and only produced one result, because finding relevant improvement and conflicting parameters was problematic. In terms of concept evaluation, the PUGH Chart method of evaluation assumes that every objective is equally important which led to many solutions being worse to the existing TTC solution of PA systems. The weighted decision matrix method of evaluation scored the solutions on a 3-point scale. A finer granularity used in scoring would give more information, which would lead to a more accurate ranking of the solutions.

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Limitations of final design

The proposed solution has many advantages over existing solutions. It provides more accessibility than the current physical barriers implemented at Bloor & Yonge station, since its purpose is to segment the platform rather than restrict the path users can take from the platform entrance to the train. Compared to law enforcement equipment such as heat-ray guns, the proposed solution is also less harmful to the user and less costly to implement.

However, one limitation of the final design is that users can fail to identify where empty sections are if their vision is obstructed by crowds. A way to mitigate this issue is to use the barriers in conjunction with LCD screens which notify users of empty sections. Another improvement is to include grooves or rollers at the base of each panel to ease implementation.

The solution is likely to succeed in the marketplace as it has applications beyond the TTC subway platforms due to its ability to be secured onto any protruding edge and adjustable length. It also has a low material cost and is easy to implement compared to existing solutions. The barriers can also be used to generate revenue by using a portion of the panels on either side as advertising space, while maintaining non-visually obstructive.

ACKNOWLEDGMENTS The authors would like to thank Jayesh Srivastava and Hyunmin Cheong for their insightful comments and clarifications during the design process.

REFERENCES Fang, Z. et al., 2003, On the relationship between crowd density and movement velocity, Fire Safety Journal, Vol. 38, No. 3, pp. 271-283. Jaiswal, S. et al., 2008, Relating bus dwell time and platform crowding at a busway station, Proceedings from the 31st Australasian Transport Research Forum, pp. 239-249. Sammons, Aidan. "Effects of Crowding." N.p., n.d. Web. 2 Dec. 2012. "Higher Subway Ridership Brings Revenue and Crowding." Allvoices. N.p., n.d. Web. 07 Dec. 2012. Sabic Innovative Plastics. "Lexan* 9030 and Lexan* 9030 TG Sheet." N.p., Jan. 2008. Web. 7 Dec. 2012.

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APPENDIX A: Concept evaluation methods

Weighted Decision Matrix

Pugh Chart

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APPENDIX B: 2-D drawing of final design