Measures to optimize pedestrian flows in connection with big events

– simulations and calculations on the example of Zurich Stadelhofen

Michael T. Nehmiz Institute for Transport Planning and Systems Swiss Federal Institute of Technology, ETH

Zurich, Switzerland michael.nehmiz@posteo.ch

Abstract—During the Zurich Festival it comes to remarkably high traffic loads of passenger. This holds especially for the time right after the end of the fire work at Saturday night, when many visitors want to go home by train at the same time. In particular, the side platform with trains heading towards Zurich HB is heavily crowded. This leads to high person densities on the platform and delayed departures of the trains. This thesis investigates measures which lead to an optimization of the pedestrian flows at Zurich Stadelhofen during the Zurich Festival. Therefore, microscopic simulations of pedestrians and trains were executed with the microscopic simulation software PTV Vissim. The goal is to assess the effect of such measures at this certain train station. The results show that with the implementation of a temporary access restriction (”dosage”) the situation at Stadelhofen can be optimized in terms of decreasing the person densities on the platform and improving the process of boarding and alighting in general. This happens on the expense of increasing travel times and high densities in front of the accesses of the train station. Additionally, it was tested whether it is possible to evaluate measures with analytical calculations. Here, it could be shown that the analytical calculations have a high potential in evaluating the access restriction at this specific train station.

Keywords—Microsimulation, Pedestrian Flows, Safety at big Events, Analytical Calculations, PTV Vissim

I. INTRODUCTION The train station Zurich Stadelhofen is located in the very

center of Zurich, close to the old town, the Zurich Lake and the Sechseläutenplatz. Due to its central and attractive location it comes to several big events in direct vicinity of the train station, e. g. the Street Parade, Sechseläuten or the Zurich Festival. Latter is one of the largest fairs in the world [1]. Especially right after the end of the firework of the Zurich Festival it comes to remarkably high numbers of pedestrians heading towards Zurich Stadelhofen and entering the train station. This results in very high person densities on the platform and a disturbed process of boarding and alighting. To tackle the high traffic loads, measures to improve the situation should be implemented. Therefore, simulations and calculations were executed and analyzed. As there are different approaches to evaluate pedestrian flows, a comparison of the microsimulation in Vissim and analytical calculations was made.

II. LITERATURE REVIEW

A. General Influences on the Pedestrian Flows As walking is the oldest way of locomotion, it is important

to understand the general characteristics of pedestrian movements: Basically, walking is the type of movement with the lowest space requirements. In upright standing position, humans need space of only about 0.2 m2. Additionally, walking is the mode of transport which is very sensitive regarding detours: Pedestrians prefer to go the direct desired path. With respect to the walking speed, it is noteworthy that the desired speed of pedestrians depends on several factors: The two main factors are the age of the pedestrian and the purpose of the trip. For example, older people have a rather lower desired speed than young people and commuters a higher speed than tourists.

The macroscopic relation of speed, density and specific flow of pedestrians is analogously to principles of the fundamental diagram of the motorized private transport: As passenger densities increase, the velocity decreases and vice versa. At a certain density and a certain velocity, the flow of pedestrians is maximized. In the literature, there are different characteristic values, e. g. for the maximum densities or the free-flow speeds. This thesis rests on the empiric values from Weidmann et al. [2][3].

There is also a big influence of the design of facilities to the pedestrian movements. This covers on the one hand the clear widths of accesses or walkways etc. and on the other hand the presence of obstacles. To gain the clear width of a pedestrian facility, one has to make deductions from obstacles and lateral boundaries. The distinction in different functions of pedestrian facilities (e. g. waiting, walking etc.) is relevant as well.

B. Measures to Influence Pedestrian Flows There is a big variety of additional measures which

influence the flows of pedestrians. Nowadays, measures to influence pedestrian flows occur mainly at events with high traffic volumes. This are for example concerts, sport events or fairs. Here, the best practice is to anticipate the crowd movements and to spot the potential bottlenecks in advance. It is also common to use barriers, fences and personnel to influence the flows or to restrict the access to certain areas.

An additional measure which influences the pedestrian flows is the application of auditive and visual signals, i. e. loudspeaker announcements and signposts. With the appropriate use of such measures one can guide the pedestrian – especially in case of emergencies – toward different exits and can thus decrease the time for an evacuation [4]. In the environment of train stations, the application of auditive and visual signals is omnipresent.

One further method to influence pedestrian flows is by adding temporal access restrictions: The approach is, that pedestrians have access to a certain area – for example train platform – only within a given time frame. This could be applied especially in the context of big events to keep safety critical areas (i. e. staircases or platforms) under a certain density limit. However, such access restriction (“dosage”) leads to an increase of the travel times for the affected pedestrians [5].

Regarding the process of boarding and alighting of passengers, one appropriate measure is to add keep-out-zones on the platform. The idea is, that boarding passengers are not allowed to enter this specific area which is highlighted with a floor signaling. At the same time, the alighting passengers have to use certain doors exclusively to leave the train. The position of the dedicated doors for the alighting passengers and the keep-out-zones on the platform correspondent. This measure leads to a reduction of the time for boarding and alighting passengers [6].

By the targeted application of adding obstacles within the design of pedestrian facilities, one can improve the flows and avoid certain undesired effects of crowd behavior. To avoid for example the clogging effect in front of doors – which occurs when there is high pressure in the crowd – it would be beneficial to implement a design element in front of the door. Additionally, the separation of opposite pedestrian streams can improve the overall flows [7].

C. Evaluation Tools In general, the usage of a microsimulation for analyzing

pedestrian flows has the advantage to replace field experiments with executing large-scale experiments. One leading tool for microsimulation is the software PTV Vissim which has an extension for modelling pedestrian flows (Viswalk). It is based on the social-force model by Helbing and Molnar [8]. Here, three forces work: The force of acceleration speeds-up the agent until it reaches the desired speed. The repelling forces preserve distances to lateral boundaries, obstacles and other agents and the attractive forces which are caused for example by ticket machines or friends.

A further possibility to analyze pedestrian flows and to evaluate measures is the application of analytical calculations. These calculations are based on empiric values from the literature, knowledge of the dimensions of facilities, knowledge of rail operations and assumptions of the inflows of pedestrians. On this basis, it is possible to estimate the person densities, the congestions and the travel times of pedestrians. Compared to the microsimulation, this approach is rather macroscopic: The behavior of single pedestrians is not taken under consideration, but pedestrians are aggregated to pedestrian flows.

III. ZURICH STADELHOFEN

Fig. 1. Location of Zurich Stadelhofen

A. Infrastructure The rail facility of Zurich Stadelhofen consists of only two

platforms. The side platform in direct vicinity to the main building serves track 1 with trains heading exclusively in direction of Zurich HB. It can be reached at ground level without crossing the tracks and is approximately 250 m long. The second platform is the middle platform with a length of 300 m. It serves track 2 and 3 and can be reached via the underpass. Inside the underpass, there are multiple shopping facilities (e. g. Coop).

B. Rail Operation There are exclusively suburban trains operating at Zurich

Stadelhofen. It is beside Zurich HB, Oerlikon and Hardbrücke the most important train station in the railway system of Zurich. The operations start at 5 o’clock in the morning and end at about 1 o’clock the next day. In the normal peak hour 40 trains are in use which means that there is an average headway of the trains of three minutes for each direction. At the weekend there are additional trains operating during the night and at certain big events like the Zurich Festival or the Street Parade, special timetables are valid.

Currently, there are three different generations of rolling stock operating at the suburban train system of Zurich and at Stadelhofen. The trains differ partially in length, number of coaches, number of doors, capacity and boarding height. Anyway, all operating trains consist of double-deck coaches which have the advantage of rather high capacities. However, all trains of the suburban train system of Zurich have only two doors per coach. This leads to longer times for boarding and alighting compared to coaches with more doors. Therefore, the Swiss Federal Railways (SBB) plan to replace the double-deck trains at a core network of Zurich with single-deck coaches with more doors.

C. Pedestrian Traffic During normal working days, more than 80’000

passengers travel via the train station Zurich Stadelhofen. Due to the fact, that the train station is located in direct vicinity of many working and education facilities, there are more inbound trips in the morning peak hour. This pattern turns in the evening peak, when there are more outbound trips. In total, the evening peak represents the maximum traffic load of a normal working day.

Due to its central location, there are several big events in direct vicinity of Zurich Stadelhofen. The largest one is the Zurich Festival every three years. The latter hosts up to 2.5 million visitors during the three days of the festival. One of the highlights of the Zurich Festival is a big firework over the Zurich Lake at Saturday night. Right after the end of the firework, many visitors leave the festival at once and head towards Zurich Stadelhofen. For this reason, the organizer of the Zurich Festival, the Zurich transport association (ZVV) and the SBB make consistently the following recommendations to destress the passenger loads of Zurich Stadelhofen:

• Purchase ticket for journey home in advance

• Stay a little longer at the festival after the firework

• Walk to Zurich HB or other train stations nearby Notwithstanding the recommendations of the above-

mentioned parties, it came to very high traffic loads at Zurich Stadelhofen after the end of the firework at the Zurich Festival 2019. In total, there were more than 15’000 pedestrians counted in the hour between 11 pm and 12 pm (see Fig. 2). This is more than twice as much than during the peak hour of a normal working day. With regard to the side platform with trains in the direction of Zurich HB, the traffic volumes are particularly high: With almost 10’000 passengers, the traffic volumes are almost four times as high as during the normal evening peak. The middle platform – with trains in opposite direction – is not much more crowded than during the normal working days.

Fig. 2. Traffic loads of entering passengers at Zurich Festival (11-12 pm)

IV. GERNERIC MODELS To handle the big traffic volumes that occur at Zurich

Stadelhofen at the Zurich Festival and to ensure the safety of the visitors, measures that influence the pedestrian flows seems to be necessary. Those measures were discussed in the literature review. But before the measures are simulated and analyzed on the environment of Stadelhofen, generic models were introduced to test the general effect of each single measure in an un-disrupted environment. Additionally, the question needs to be answered, whether the measure is suitable for Stadelhofen and whether it can be simulated properly in Vissim.

A. Keep-Out-Zones The approach of the keep-out-zones is to block certain

areas on the platform for the boarding passengers to provide space for the alighting passengers. At the same time, the alighting passengers have to use dedicated doors to leave the train. Consequently, the doors of the train are used only one-way. The analysis contents two dimensions of five different scenarios each: One dimension is the ratio of waiting areas and keep-out-zones. The second dimension is the ratio of boarding and alighting passengers. This results in totally 25 scenarios. The analyses of keep-out-zones showed that the times for boarding and alighting of passengers can be improved. Therefore, the ratio of waiting area and keep-out-zone needs to correspond to the ratio of boarding and alighting passengers (see Fig. 3).

Fig. 3. Times for boarding and alighting with keep-out-zones

B. Temporary Access Restriction (“dosage”) For the simulation of the dosage, a traffic light was

implemented to Vissim. This blocks the boarding passengers from entering the platform. Different scenarios with variation of the passenger inflow and the headway of the trains were executed. To solely obtain the effect of the dosage, alighting passengers were not simulated.

The simulation shows, that the person densities on the platform can be decreased by the added dosage. Here, the duration of the dosage determines the number of passengers reaching the platform and thereof the density. Anyway, the person density increases upstream, i. e. before the dosage. Depending on the supply of trains and the initial flows of boarding passengers, the congestion in front of the dosage either remains over the long-term or disappears. For the simulations without access restriction, the train needs to have a configuration regarding the dwell time, i. e. a definition of how long the boarding of the train is possible. Otherwise, the train would wait for all arriving passengers to arrive until its capacity constraint is reached and “infinite streams” of boarding passengers would occur. Additionally, it could be shown, that with the dosage, the travel times of the agents increase by about 40 % compared to the simulation without dosage. At the same time, the duration of boarding and alighting decreases significantly and counteracts the negative effect of the travel times almost completely.

C. More even Distribution of Passengers on the Platform There are different factors that influence the waiting

position of boarding passengers on the platform. One factor is the position of the access, i. e. the probability of waiting close to this access point is higher than waiting far off [9]. This assumption was taken as a basis for the generic models. In theory, the shift of the access point by adding an obstacle (as in Fig. 4) leads to changed probabilities of the waiting positions. For the simulation with Vissim the implementation of an obstacle is not necessary as the distribution of passengers is done with the probabilities of the waiting position. Therefore, the platform is divided into ten smaller waiting areas.

Fig. 4. Probailities for more even distribution on platform

The simulation of this improved distribution on the platform showed, that the effect of changing the possibilities of the waiting positions is rather low. However, there is a positive influence on the time for boarding and alighting of the passengers which can be decreased. This effect occurs predominantly at higher traffic loads.

V. SIMULATION OF STADELHOFEN The generic simulation proofed, that the implementation of an access restriction as well as the more even distribution have a positive effect on the passenger flows in terms of lowering the densities on the platform and accelerating the time for boarding and alighting of the passengers. For the simulation of the optimization of passenger flows at Stadelhofen, these two measures will be combined. Due to the increased densities, the keep-out-zones will not be implemented to Zurich Stadelhofen.

A. Setup of the simulation After the Vissim model was built, the pedestrian inflows are – based on the counts from 2019 – initialized. Additionally, the supply of public transport is implemented, i. e. the rolling stock and the schedule were created. The routes from the boarding passengers include the waiting position. Here, the assumption from before is valid, that the passengers tend to wait close to the access points instead of distributing evenly. In total, there are nine waiting areas created on the side platform in the Vissim model.

B. Initial State The simulation of the initial state shows, that there occur

very high densities on the platform. Here, the person densities refer to the waiting areas. The maximum observed value is 2.75 persons per square meter (see Fig. 5). As the densities highly depend on the schedule of the trains, the maximum density occurs when the headways of the trains are the longest (seven minutes).

Fig. 5. Person densities on waiting areas over time

For the process of boarding and alighting of passengers the train requires a fixed dwell-time. Otherwise, “infinite streams” of boarding passengers would occur analogously to the observation at the generic simulation. The implemented dwell time is – with respect to the time schedule – determined to be exactly 120 seconds. Thus, it comes to a rejection of boarding passengers in the simulation.

The travel time is measured from the initialization of the agents until it enters the public transport vehicle. It comes to an average travel time of all boarding passengers of 181.4 s. Here, more than 50 % have travel times between 20 and 120 seconds. This represents the passengers who arrive “just in time”, i. e. after the waiting passengers have entered the train. Additionally, it could be proofed that the schedule respectively the headway of the trains has a big influence on the travel times: With a uniform schedule (one train every 120 s), the average travel time decreases by approx. 40 %.

C. Optimization The optimization of the simulation contains of three access

restrictions (one at each access) and a more even distribution of the waiting passengers on the platform. The objective is to lower the person densities on the platform and improve the process of boarding and alighting. Furthermore, the congestion – which will occur at the access restriction each time it is closed – is supposed to disappear at the end of the simulation.

For the access restriction, a repeating “dosage pattern” is introduced. It ensures, that passengers only get to the platform in a certain time frame, i. e. when the train has not arrived yet. As soon as the train arrives, the access will be restricted. In Vissim, the restriction is simulated with a repeating traffic light configuration. To apply this dosage pattern, the train schedule needs to be unified which result in train headways of 200 s. The inflows of the passengers are the same as in the initial state as well as the operating rolling stock.

The main results from the simulation basically cover the results from the generic models: The person densities on the platform can be significantly decreased. The maximum observed density is 1.4 P/m2. At the same time, the process of boarding and alighting passengers is improved. Here, the previously observed “infinite streams” disappear. Instead, all waiting passengers are able to enter the train within the desired cycle.

Nevertheless, the travel times of the agents increase by about 6 % compared to the initial state. It must be remarked that the negative effect of the dosage on the travel times is even higher. However, the adjusted schedule with uniform headways counteracts the negative of the dosage. Furthermore, the frequency distribution shifts, i. e. becomes more homogenous (see Fig. 6).

Fig. 6. Travel times of the initial state and the optimization

Additionally, the times for boarding and alighting decrease with the implemented pattern. But, as there is a fixed dwell time in the initial state, a comparison is rather inappropriate. Anyway, the temporary congestion which occurs upstream of the dosage disappears over time.

To test the maximum capacity of the side platform, the optimized Vissim simulation was used. Therefore, the inflows were increased stepwise. Both the dosage pattern and the constraint of having no long-term congestion upstream have to be fulfilled. As a result, the inflows can be increased by about 40 % which gives in total 14’000 boarding passengers.

VI. ANALITICAL CALCULATION OF STADELHOFEN Besides simulating the situation at Zurich Stadelhofen, the

approach was made to make analytical calculations. Here, the goal was to test, whether it is possible to evaluate measures with manual calculations. In general, the analytical calculation is based on empiric values which represent the pedestrian traffic. The specific flow rate, for example, indicates, how many passengers cross a section of one meter per second. Furthermore, the dimensions of the train station need to be known. At last, the inflows of passengers and the probabilities of waiting areas needs to be assumed. Here, the same values from the simulation were used to allow a comparison of the results at a later stage.

The analytical calculations were done in an excel-file with a time resolution of one minute. That means, that for each minute the conditions of the different areas of the train station was calculated. These areas are:

• Inflows (how many passengers arise?)

• Access point (if the dosage is active, no one can continue to the waiting position and a queue is formed)

• Waiting areas (How many people are at the different waiting areas and how high is the person density?)

• Train (If there is a train available, the waiting areas will be cleared. If not, the passengers remain at the waiting area)

With this approach, the densities on the waiting areas can be calculated. Furthermore, the upstream congestion at the access points can be detected and from this one can derive the travel times of the boarding passengers.

With regard to the person densities, the analytical calculations deliver similar results as the simulation. In general, the calculated values are slightly lower (max. density 2.2 P/m2), but the shape of the figure representing the person densities on the waiting areas is the same (see Fig. 7).

Fig. 7. Person densities initial state (analytical calculations)

Additionally, there is certain potential to extend the analytical calculation: One could – for example – implement a border value of the density to gain information about the optimal dosage. That means, that the activation of the dosage rather depends on the current person densities on the platform than on the pre-defined pattern. This could be implemented to the exec-file with adding an if-condition comparing the current densities on the platform with the desired maximum density. This implementation requires a sharp time resolution.

The analytical calculation of the maximum capacity of the side platform (in passengers per hour) is based on the empiric values of max. specific capacity and door capacity. It shows, that with the application of these values, a maximum capacity of 20’700 passengers per hour can be reached.

VII. SYNTHESIS

A. Measures With the implementation of a dosage and a more even

distribution of the passengers on the platform, the passenger flow will be affected. These effects were shown with a microscopic simulation and analytical calculations. The main results of the comparison of the initial state and the optimization are summarized in Table 1.

TABLE I. COMPARISON OF RESULTS FROM BOTH EVALUATION TOOLS

Indicator Summary of results

Scenario Simulation Analytical calculation

Maximum person density Before

After

2.75 P/m2

1.40 P/m2

2.20 P/m2

1.32 P/m2

Average travel time Before

After

181.4 s

192.0 s

121.2 s

356.3 s

Average dwell time Before

After

120 s

75 s

120 s

120 s

Maximum capacity 14'000 P/h 20'700 P/h

The realization of the suggested measures can be ensured with using barriers or fences as “dosage doors”. This needs to be operated with personnel. Additionally, the access restriction and the arrival of the trains needs to be coordinated. This requires a simultaneous command to close the access. The uniformed schedule which was assumed for the simulation and the analytical calculations, seems to be challenging to realize: As the headway is exactly 200 seconds, this precision is hardly feasible. Nevertheless, the schedule does not need to be completely uniform but too long and too short headways should be avoided, which seems possible to realize.

To gain a more even distribution of the passengers on the platform, the implementation of obstacles was discussed. In the case of the Zurich Festival, the space consumption of such construction elements would shorten the available space. Therefore, the distribution of the passengers can be realized with personnel which guides the pedestrians towards certain areas. Beside the measures of the optimization, a good communication in terms of signposts and loudspeaker announcements is necessary.

In general, the measures can be adapted to other events and train stations. The implementation of a dosage would make sense for cases with high traffic loads (e. g. sports event, Street Parade, Fasnacht) and if the spatial conditions permit. The adaption to normal traffic loads (i. e. peak hours) is rather unsuitable.

B. Evaluation Tools The most important results – obtained from both the

simulation and the analytical calculation – are listed in Table 1. It shows, that both evaluation tools provide similar results for the person densities. However, the analysis of the travel times brought different results. A comparison of the dwell times is difficult, as it was defined to be 120 s in the simulation without dosage and the analytical calculation. Nevertheless, it shows that with the dosage, the process of boarding and alighting can be improved. The maximum capacity of the side platform calculated analytically appears to be very high and should be used as a maximum benchmark only.

With the analytical calculation, the effort and the outcome are well balanced as it allows to gain fast and easy plausible results. The initial effort to create the model in Vissim is rather high but once the model is built, changes are easily possible and different scenarios can be applied. One the other hand, to represent the output, it has to be transferred and due to the rather high number of agents within the simulation, the duration of the simulation is quite long. Nevertheless, the level of detail of the provided data of the simulation is very high and the visualization of traffic processes is possible.

The analytical calculation can be applied very easily to both other events (e. g. normal peak hour) and other train stations. This is because it refers to the usable width and not certain locations. The simulation can also be applied to other events but not to other train stations, because the model is very unique and cannot be transformed to other train stations.

VIII. CONCLUSUIN This thesis showed that the appropriate implementation of

measures can improve the passenger flows at a certain case, i. e. during the Zurich Festival at Zurich Stadelhofen. It was shown in the microsimulation and with analytical calculations, that with the implementation of a dosage the maximum densities on the side platform can be remarkably reduced and the process of boarding and alighting is improved. Nevertheless, the travel times of the passengers increase, and higher densities occur upstream, i. e. the person densities are shifted. However, as higher densities in direct vicinity of the rail track can be avoided, the safety of the passengers can be improved.

Additionally, it could be shown that both evaluation tools (microsimulation and analytical calculations) have their advantages and disadvantages. In general, the question needs to be answered, which level of detail is desired. For the case of the Zurich Festival the (macroscopic) approach of analytical calculations appears to be sufficient, due to the fact that interactions of single pedestrians play a tangential role.

ACKNOWLEDGMENT I would like to thank my supervisors Dr. Ernst Bosina and

Thomas Spanninger who supported me throughout the whole process of this master thesis. I also express my gratitude to Prof. Francesco Corman who hosted this work at his chair and contributed his expertise to this thesis. Further thank goes to Beda Büchel for valuable inputs.

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