# Exploring Interactions with Tangible and Actuated Tokens on a Shared Tabletop for Railway Traffic Management Control Centres

Maudeline Marlier, Nicolas Renoir, Martin Hachet, Arnaud Prouzeau

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Maudeline Marlier, Nicolas Renoir, Martin Hachet, Arnaud Prouzeau. Exploring Interactions with Tangible and Actuated Tokens on a Shared Tabletop for Railway Traffic Management Control Centres. TEI 2025 - 19th International Conference on Tangible, Embedded, and Embodied Interaction, Mar 2025, Talence, France. 10.1145/3689050.3704938 . hal-04891924

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# Exploring Interactions with Tangible and Actuated Tokens on a Shared Tabletop for Railway Traffic Management Control Centres

Maudeline Marlier

SNCF DTIPG

Saint-Denis, France

Inria

Bordeaux, France

maudeline.marlier@sncf.fr

Martin Hachet

Inria

Bordeaux, France

CNRS

Bordeaux, France

martin.hachet@inria.fr

Nicolas Renoir

SNCF DTIPG

Saint-Denis, France

nicolas.renoir@sncf.fr

Arnaud Prouzeau

Université Paris-Saclay, Inria, CNRS

Paris, France

arnaud.prouzeau@inria.fr

<figure><img src="image_2.png" /><figcaption>Figure 1: Prototype of tangible interactions for crisis management in railway control centres</figcaption></figure>

## Abstract

While control centres are increasingly incorporating digital tools, particularly with the expanding train traffic worldwide, the role of humans remains essential. This is particularly true in case of crisis, where operators with different expertise need to collaborate to make critical decisions. We visited different control centres to observe how operators work, especially in crisis scenarios, and identify the limits of the current approaches. Inspired by this, we developed a prototype to investigate the use of actuated tangible tokens on a tabletop to visualise and explore different solutions to

resolve incidents. To gauge the implications and opportunities of our approach, we performed a qualitative study with 37 operators in a high-speed train control centre. Our results suggest that actuated tangible tokens on a shared display constitute a promising tool for information sharing, context understanding, problem solving and collaboration.

## CCS Concepts

* **Human-centered computing → User interface management systems.**

## Keywords

Collaboration, Crisis, Tangible, Shared Tabletop, Control Centre, Training

## ACM Reference Format:

Maudeline Marlier, Nicolas Renoir, Martin Hachet, and Arnaud Prouzeau. 2025. Exploring Interactions with Tangible and Actuated Tokens on a Shared Tabletop for Railway Traffic Management Control Centres. In *Nineteenth International Conference on Tangible, Embedded, and Embodied Interaction*

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TEI '25, March 04–07, 2025, Bordeaux / Talence, France

© 2025 Copyright held by the owner/author(s). Publication rights licensed to ACM.

ACM ISBN 979-8-4007-1197-8/25/03

https://doi.org/10.1145/3689050.3704938
(TEI '25), March 04-07, 2025, Bordeaux / Talence, France. ACM, New York, NY, USA, 12 pages. https://doi.org/10.1145/3689050.3704938

# 1 Introduction

Rail is a popular and useful way to reach distant cities located on a network over one or several close country. Due to the challenging climate crisis we are facing, rail transport is a valuable opportunity for replacing flight habits and may contribute to a more sustainable world. However, the rail network can be complex, dense and thus challenging to manage. The French rail network, for instance, is composed of more than 3000 stations and is used by 15000 trains every day. A single incident on this network can provoke a cascade of events that can lead to important disruptions. On Friday at 27th of July 2018, a fire in a power substation in the south of Paris caused a significant power cut in the Montparnasse train station, the station in charge of most of the traffic with the west of France (Brittany and south-west). As a consequence, the station had to be closed which led to the majority of trains being either rerouted to different stations or cancelled, which in turn created substantial disruptions in train services, affecting almost a third of the country with numerous trains experiencing delays exceeding three hours. It took almost a week for the situation to come back to normal, impacting 100,000 passengers per day during three days and costing millions to SNCF, France's national state-owned railway company [25]. Normal traffic may resume only 10 days after the incident.

To minimise the occurrence of such situations and ensure quicker response times, the network's traffic is monitored and controlled by operators stationed in over 300 control centres, each responsible for managing traffic at stations, on high-speed, or regional lines. The increasing amount of data generated by the growing presence of emerging technologies (e.g. digital trains), the opening up to the competition that brings up more stakeholders and the desire to increase the number of trains are putting more and more pressure on operators, especially in critical situations.

In order to understand how such control centres could perform better, we visited different centres. These allowed us to understand better how they are organised and how operators manage both routine operations and critical events. No control centre is identical, however as a general rule, the control room is set up as a desk with multiple screens per operator, usually facing a large vertical screen to display an overview of the monitored network. A study by Prouzeau et al. suggests that such a layout supports routine operations, in which collaboration between operators is sparse and loose, but is not optimal when dealing with a critical event that requires planning and close collaboration [58]. This is supported by our observations: operators have some difficulties sharing information or maintaining an appropriate level of awareness of the situation when disruption happens on the network.

Inspired by projects proposing tangible interactions on shared screen for collaboration [5, 38], we explored a solution that take benefits from both a shared display and physical objects that can be manipulated, illustrated in Figure 3. We decided to use actuated tokens (i.e. tokens that can move by themselves on the table and be moved by operators) to allow the system to communicate a potential solution to the operators, but also to provide an easy way to replay any alternative ones previously proposed. As such a system would represent an important change in operators' work environment and work method, we wanted to first assess their acceptance of the use of actuated tangible interactions on a tabletop and explore with them how it could be integrated with their current practices and setup. Therefore, we developed a prototype and performed expert feedback sessions with 37 operators including 34 in a control centre in charge of the high-speed trains in the west of France and three crises management experts. Our results of this qualitative study suggest that actuated tangible tokens on a shared display could help operators during crises for information sharing, context understanding and time saving.

Our contributions are: (i) The use of a digital tabletop interface with actuated tangible tokens to enhance railway control operations, which could be generalised to other complex problem domains that require collaborative decision-making and real-time situational awareness. (ii) A qualitative study with 37 operators to collect feedback on the advantages and the possible acceptability of this system in control centres.

# 2 Related work

We reviewed the literature on control centres and their methods and tools for solving problems. This section investigates four categories of works. First, we analyse studies on control centres and their users' interfaces. Second, we explore broad use cases of tangible interactions, highlighting benefits such as improved user engagement and more intuitive interactions. Third, we examine specific applications of tangible interactions within control centres, emphasising their impact on situational awareness, workflow efficiency, and error reduction. Finally, we review the use of actuated tangibles in various fields to understand their benefits and potential applications in control centres. Through this literature review, we aim to gather insights and best practices to inform the design and implementation of control centre systems.

## 2.1 Control centres

In the early 1900s, with the rise of mass production facilities and the development of transport networks (e.g., subway, train, boat), control centers began to emerge to monitor these systems and intervene in case of failure [8]. Without computers or screens, physical representations and controls were common in the first control rooms. These often included large physical representations of networks and indicator lights to display system status. For example, in 1931, the London electricity distribution network used such a system [55, 64], and the control center for the Panama Canal locks featured a large table with columns and gauges representing water levels in each lock [63]. Some control rooms also used physical objects to represent moving elements in the system, often manually adjusted by operators. In air traffic control, for instance, controllers would place tokens representing aircraft on a large map and move them as pilots reported their positions [67]. This technique is still in use
today on aircraft carriers with the 'ouija board', which employs tokens to represent aircraft and their positions on the ship [32, 68].

Over the years, with the widespread adoption of digital technology, the growing volume of data, and the increasing use of automation, control centers have shifted towards individual workstations for operators. While shared displays remain common, they primarily provide an overview visualization of the system, with little direct interaction from the operator, impacting thus, the global understanding of the system, but also how operators collaborate [19]. Dos Santos et al. [20] studied nuclear power plants to underscore the significance of incorporating the human factor in interface design and specified that these interfaces must be situation-specific. This highlights the intricate nature of centres that demand a tailored approach for each case because these interfaces allow to understand a context. This importance of context have been study also in nuclear plant application [11] and in subway control centre [12]. In these cases, user interfaces are a major asset for crisis management and the majority of operators in control centres mainly interact with their processes via desktop computers [13] often accompanied by wall displays in the room.

Other papers present mental workload in road traffic control room [69], conflicts resolution and non-verbal communication in air traffic control centres [10, 46] or a global presentation of how different control centres work [56].

## 2.2 Tangible interactions

The physical world provides multi-sensory experiences and enhances natural social interactions. It introduces the concept of embodied cognition, which refers to thoughts (cognition), emotions (emotion), and behaviours (body) based on our sensory experiences and bodily positions [24]. This world sometimes encounters limitations that can be overcome through the digital world. Ishii and Ulmer [66] define the Tangible User Interface (TUI) as an interface that "gives physical form to digital information, employing physical artefacts both as representations and controls for computational media". Tangible interactions assist in structuring spatial information for verbal expression, contribute to conceptualise a verbal message thanks to gestures that play a key role in cognitive activity [1] and help when communication is difficult with words [15]. Several projects aim to study TUIs in different domains such as education [5, 35], music [2], geology [17], urban planning [31] and show that the main benefits of tangible interactions are motor memory [37], learnability [60], the possibilities of conveying the rich meanings in social settings [29] and intuitiveness [30]. Klemmer et al. [37] specify that physical bodies play a central role to interact in the world. This leads us to think that communication and collaboration are closely related to gestures. Tangible interactions have been also studied specifically with multi-user collaboration [4, 5, 16, 23, 33] or collaborative visual analysis [22] on large display, horizontal or vertical. Indeed, horizontal displays provide sharing data [27], and help for situation awareness [38] by enhancing the understanding of what others are doing. Gestures, talk and visible artefacts contribute to produce meaning for collaborative use [28]. Tangible tabletop systems have been developed also to allow users to interact with modeling and simulation. In the case of molecule modeling or in biology, TUI seems to have a remarkable

effect on the engagement of several people during collaboration and conversation to make decisions [26] and facilitating an understanding of complex systems and supporting collaboration [48].

## 2.3 Tangible interactions and shared surfaces in control centres

As mentioned at the beginning of this section, physical controls and representations were widely used in early control rooms before being replaced by purely digital systems. Recently, however, researchers have been exploring ways to reintroduce them in control rooms this time in symbiosis with digital systems with tangible interaction.

In aeronautics, Letondal et al. [43] explored a way that mixes numeric and physical environments using paper to keep gestures and desktop computers to keep digital benefits. They developed a system with augmented reality, digital pen, projection and screens and found that physical tokens act both as representation of mental tokens and as tangible artefacts for interacting with augmented features. However, one of the limitations of the desktop-based approaches is that computer screens can create difficulties for operators because it creates a lack of group awareness and hinder the ability to observe what others are doing [13]. In road traffic control centres, Prouzeau et al. [57] used a vertical shared display like wall displays to share information and to allow operators to collectively act on a comprehensive representation. Butscher et al. [14] show that wall displays can facilitate non-verbal collaboration in control room. Shared display can also be horizontal to easily put physical objects on the table and add information through projection. Such setups have shown benefits in non-time critical situations like in military training applications [34], in campus microgrid management [22], and also in crisis management [6, 18, 39, 49].

In our prototype, we investigate the use of tangible tokens on a horizontal tabletop for crisis management in railway control centres focusing on actuated tangible tokens.

## 2.4 Actuated tangible interactions

Actuated tangible interactions provide to go further by adding dynamic human-computer interactions. This concept began to emerge with some works such as the Actuated Workbench of Pangaro et al. [53]. It is further taken up to demonstrate that they enable new types of interactions [40, 52, 54], can be dynamically reconfigured [51] and can be used in many domains [35] as physics education, explorable mechanism, tangible gaming for children, and in-situ robot programming via sketching. Actuated tangible interactions have been used in education [70], data visualisation [41] or to work on social interactions [36].

The use of actuated tangible tokens for collaboration have been study for multi-user collaboration in classroom [35], planning in crisis management teams [18] and for remote collaboration because tokens are moved by the computer as if the remote person was moving it [61, 62]. To our knowledge, we did not found many researches about actuated tangible interactions in control room for crisis management.
## 2.5 Summary

Control centres in industries like aviation, nuclear power, and road traffic management rely on complex systems that demand continuous monitoring and rapid response to issues. These environments, heavily dependent on digital interfaces such as desktop computers and wall displays. They often face challenges related to group awareness, communication, and collaboration among operators, thus impacting effective crisis management and decision-making.

Tangible User Interfaces (TUIs) offer a potential solution to these issues by providing physical forms to digital information, enhancing multi-sensory experiences and supporting embodied cognition. TUIs allow operators to interact with digital data through physical objects, facilitating more intuitive and collaborative interactions. Research has shown that TUIs can improve situational awareness, help in structuring spatial information, and enhance verbal and non-verbal communication, making them valuable in control centre settings.

While TUIs have been explored in various domains such as education, music, and urban planning, their application in control centres is still emerging. Notably, actuated tangible interactions—where physical tokens are dynamically controlled by computational systems—present a promising yet underexplored avenue. These interactions can reconfigure dynamically, providing new ways for operators to collaborate and interact with data.

Our investigation focuses on the use of actuated tangible tokens on a horizontal tabletop for crisis management in railway control centres. This approach aims to leverage the benefits of TUIs and actuated tangibles to enhance collaboration, situational awareness, problem-solving and decision making.

# 3 Observations on the field

## 3.1 Train lines control centre

In addition to the exploration of the state of the art, we also conducted a field study to better understand railway control centres. We visited 7 different train line control centres located in the Paris and Bordeaux areas. Most of our visits lasted more than three hours in which we observed the operators. Following a semi-structural interview process, we asked them questions about their work in general, the current situation and past situations in which they encountered major incidents. There are, of course, differences between the control centres we visited, but the setup and layout was similar in most cases. The number of operators varies according to the area supervised but there are around 15 operators who oversee real-time traffic and address disruptions. Each operator is stationed behind an array of screens (ranging from 6 to 8), equipped with mice, keyboards, and telephones. A large display, positioned in front of the operators, provides an overview of the situation of the network as shown in Figure 2.

Operators are divided into three specific positions. The first one are in charge of the overall monitoring of the traffic and its perturbation (e.g. assessing the delay of a train and its impact on the other) and of coordinating the work of the two other positions, but also of the communication with the other control centres. They are also in charge of following up on incidents when they happen and they make the final decision on how to resolve them. The second one are charge of the management of the resources used by the

<figure><img src="image_3.png" /><figcaption>**Figure 2: Picture showing a railway control centre in Paris. In the forefront we can see a standard operator's positions with multiple screen and in the background we can see a large wall display showing an overview visualisation of the network.**</figcaption></figure>

train company which consist mainly of staff (train managers<fnref n="1" /> and drivers) and of trainsets<fnref n="2" />. There are many rules to follow, for train staff to be allowed to perform a trip as well as for trainsets to be allowed to be used. The operators in this position must make sure that both staff and trainsets respect these rules at any time. The third one are responsible for implementing support measures for passengers and disseminating information to them. They provide tools for station's information, phone applications, notifications or website.

## 3.2 Crisis management

During normal operations, control centres operators primarily monitor the network on their screens with minimal verbal communication. However, managing incidents demands actions and modifications on the traffic (e.g. add, remove or reroute trains), requiring closer collaboration. In our observations, we noted that during a major incident involving abandoned luggage and a station evacuation, information dissemination was inconsistent. Some operators missed initial updates and had to be informed later, while experienced staff inferred details not explicitly communicated.

Operators explored solutions by consulting digital tools and discussing options, often verbally across the room. This informal communication, while beneficial for awareness, also led to misunderstandings and potential errors. For instance, a misheard train number caused confusion. Critical decisions were not centrally documented, relying on operators' notes and memories. Implementing a chosen solution requires considerable external communication and data input, with operators frequently seeking validation from their colleagues.

The lack of a centralised system for tracking information and decisions, combined with the noisy environment, hindered effective collaboration and situation awareness. This also impacted information transfer during shift changes, where critical details were shared verbally, risking inaccuracies. The room layout further complicated

<footnote n="1">¹A train manager is responsible for comfort, safety and information for travellers on board and in train stations</footnote>

<footnote n="2">²A trainset consist of carriages coupled together to form a unified set of equipment.</footnote>
communication, requiring operators to stand or speak loudly, which could lead to information loss.

Table 1 summarises all the difficulties observed in control centres and details the consequences for operators.

<table><caption>Table 1: Summary table of difficulties observed in the operational centres and their consequences</caption><thead><tr><th></th><th>Observations</th><th>Consequences</th></tr></thead><tbody><tr><td>Communication</td><td>- Missed Updates<br>- Late Notifications<br>- Unspoken Details</td><td>- Information Dissemination<br>- Misunderstandings</td></tr><tr><td>Informations not Centralised</td><td>- Lack of Centralized Documentation<br>- Information Transfer During Shift Changes</td><td>- Risk of Inaccuracies from Operators' Notes and Memories</td></tr><tr><td>Implementing a Chosen Solution</td><td>- External Communication and Data Input<br>- Validation from Colleagues</td><td>- Hindered Effective Collaboration and Situational Awareness</td></tr><tr><td>Control Centre Layout</td><td>- Noisy Environments<br>- Verbal Discussions Across the Room</td><td>- Information Loss</td></tr></tbody></table>

## 3.3 Real-time optimization algorithms in control centres

In the process of examining control centres, we engage with experts in crisis resolution, along with engineers and researchers who are developing future systems for these centres. They focus particularly on creating algorithms to enhance decision-making processes using data from past incidents and scenarios developed by experts from recurring incidents. With their real-time optimization algorithms, operators would be able to query the system for a certain number of resolution scenarios to help them make a decision on how to solve a current incident [3]. These scenarios are designed to minimize key metrics, such as costs for the company, the number of trains affected, and overall delays. The use of such algorithms can be a great help for the operators, it is, however, important to make sure that it does not supplant the decision-making role of operators. To keep operators in the loop, they must understand why the system proposes this solution [42], but also to allow them to adapt and modify a proposed solution. As we saw in our observation, the operator's experience is important in the understanding of one incident and how to solve it, and it is not clear yet how this experience would be passed to the algorithm itself. The solution we propose in this paper will thus take this type of algorithm into account and consider that the system, as well as operators, can propose solution to an incident.

## 4 Prototype

Our sessions of observation suggested that operators faced challenges regarding information sharing, communication and thus decision-making, especially in critical situations when incidents happen. Also, new real-time optimization algorithms will change how operators perform their tasks. In section 2, previous works show that tangible interaction on a shared surface is beneficial for

collaboration: it improves group awareness and helps the communication of spatial information. With all this, we believe that it could be an interesting solution to assist operators when solving a crisis situation by using actuated tangible interaction on a shared display.

## 4.1 User-centred design

We used a user-centred design process with three iterations. In the first iteration, we paper-prototyped several ideas by building small paper boxes to simulate actuated tokens (see Figure 3a), then we used actual tangible tokens that were static (and was moved by the person demonstrating the prototype) (see Figure 3b). In the last iteration, we implemented a functional and interactive prototype with actuated tokens (see Figure 3c). The first two iterations were demonstrated and validated with feedback sessions with one expert in crisis management from the French train company. In this section, we will focus on presenting the last version of the prototype (see Figure 3c) schematised in Figure 4. This final prototype was used to perform the feedback sessions with the experts.

## 4.2 Design of our prototype

Our final prototype is composed of one tabletop that displays an overview of the situation: a spatial representation of the network with the train on it, moving in real-time<fnref n="3" />. For the spatial representation, we used an already existing rail diagram since it represents the prevailing practice among operators. Trains are represented by square on the network with their identification on the side (see Figure 5).

It would not be possible to use a tangible token to represent every trains on the network. First, it would require a high number of objects as there are many trains running at the same time (between 40 and 80 trains), and it would also need some on a side to represent trains that are not on the network but could be used in case of a breakdown. Then, it would represent a lot of visual clutter and noise. Finally, other moving entities are interesting to consider and visualise when dealing with an incident, for instance, busses that can be used to recover people from a stopped train, and thus should be represented too (increasing again the number of physical objects on the table). For these reasons, and because we focus on the context of critical situation, we choose to use tangible actuated tokens to represent moving entities involved in an incident and its different solutions.

## 4.3 Interactions

When the traffic is normal and there is no incident, there would then be no tokens on the table, they would be stationed on the side of the network visualisation. Let's now consider that a train stops between two stations because of a technical failure. The alarm in the system would then trigger a token to roll on the network visualisation and position itself on top of the virtual representation of the stopped train. The system then computes a number of solutions that operators can use to solve this incident<fnref n="4" />.

These solutions are then presented on the right-top corner of the tabletop with the list of steps to implement them. In addition, an

<footnote n="3">³Real-time means that trains move on the screen at a realistic speed. The traffic in the prototype is simulated and not a clone of the real-time traffic.</footnote>

<footnote n="4">⁴We used solutions that could be proposed by real-time optimization algorithms.</footnote>
<figure><img src="image_4.png" /></figure>

<figure><img src="image_5.png" /></figure>

<figure><img src="image_6.png" /><figcaption>Figure 3: Three iterations of prototypes: (a) first iteration of the prototype created with paper; (b) second iteration in which we used projection and static tangible tokens; (c) third iteration with projection and actuated tangible tokens.</figcaption></figure>

actuated token positions itself on top of each solution, it represents the moving entity involve in this solution (see Figure 5a).

To visualise one of the proposed solutions, the operators can double tap on one of the solution token (see Figure 5b). The selected token will then demonstrate on the network the visualisation of the solution. In the case where the solution is to take a train from a near-by train station to push the stopped train, the token will roll to the train station, an ID will appear on top of it on the screen showing that it is a new train, and it will follow the rail the train would have to follow to reach the stopped train and then push it. After demonstrating the solution, the token goes back to its initial position on top of the description of the solution. The speed of the token is not realistic compared to the speed of the train which allows the solution to be demonstrated in accelerated form (the real solution might take hours, it would not be usable not to accelerate it). When a solution is demonstrated, the speed of the virtual representation of the other trains are accelerated accordingly to be coherent with the speed of the token.

On the side of the network visualisation, there are tokens that are not assigned yet to an entity. The operators can use them to propose their own solution. To do so, they have to take one and shake it (see Figure 5c), in order to enter into the edit mode. All the actions done with it on the table are then recorded and associated with the new solution. The operator can assign the token to an already riding train by directly putting the token on top of it, or they can put the token on a train station or technical centre. Then a pie menu opens around it and the operator can select, by rotating the token and tapping, a train that is available there (see Figure 5d). When the token is assigned to a train, the operators can slide it on the network to record its path. When arriving at the stopped train, the operator needs also to move it in the right direction to simulate the pushing or pulling action. The new solution appear on the display to allow operators to compare it to the solution suggested by the system (see Figure 5e). It is possible to edit a solution by shaking the related token. Finally, the operators can delete a solution by putting the token associated in the "garbage" area at the bottom-right corner (see Figure 5f).

<figure><img src="image_7.png" /><figcaption>Figure 4: Schema of the prototype setup we implemented, with a projector for top-down projection and actuated tangible tokens.</figcaption></figure>

## 4.4 Scenario

To demonstrate a concrete use of our prototype, we draw up a scenario inspired by a real event with a crises-expert in order to allow operators to project themselves into the use of such a tool with a situation they have already experienced or could have experienced (real stations, real train numbers and realistic solutions). In this scenario, a train is stopped in the middle of the tracks between two stations. According to the expert, three mains solutions come up : (i) use the next train to push the blocked train, (ii) find an other train to push or to pull the blocked train, (iii) evacuate passengers onto another train or into buses. The first solution (i) will be presented as a solution suggested by an the system. The demonstration starts with the incident described previously. At the beginning of the incident, the system proposes a solution (solution (i)).

## 4.5 Implementation

We use Sony Toio<fnref n="5" />, compact robots designed for tabletop use. These cube robots have dimensions of 3.2 cm x 3.2 cm x 2.5 cm and the tracking is done with a pattern-printed tracking mat covers 55 cm × 55 cm and a camera on each robot that deliver position and orientation with a 1 mm error. They have a button and can detect

<footnote n="5">⁵https://www.sony.com/en/SonyInfo/design/stories/toio/</footnote>
<figure><img src="image_8.png" /><figcaption>Figure 5: Photographs of the main interactions on the prototype: (a) an incident occurs, tokens move on the mat, (b) operator double taps on the token to play the solution, (c) operator shakes the token to create a new solution, (d) operator taps to open a menu, rotates the token to select an item in the menu and taps again to validate, (e) operators can compare two solutions, (f) operator places the token in the red area to delete the solution.</figcaption></figure>

shake-up for user-input. On the other side for output, they have a led, a loudspeaker for sound and it's possible to control speed, position, orientation of the TOIO. All the specifications of the TOIO are detailed here<fnref n="6" />. For the controlling algorithm, we adapt an open-source library on Unity<fnref n="7" /> which works on MacBook with Bluetooth to communicate with TOIO. We change the code to control several TOIO at the same time and developed all the interactions and the projection layout. As a tabletop, we used a classic table with a projector on top of it with a resolution of 1080p and hang 170cm above the table. For calibration, we project 4 squares and put a TOIO in each to get their position back. In this way, we create a match between TOIO's position on the mat and projection position.

# 5 Feedback Sessions with Experts

A system using the technology presented in the previous section would represent a significant change in the control room setup and in the operators' activities and tasks. In order for it to be accepted by operators, it is important to be compatible with the tasks at hand, and to bring advantages and not too much complexity [65]. To assess such aspect and following a user-centered design methodology, we chose to perform feedback sessions on the prototype with end-users, i.e. railway operators. Instead of using a finalised system for this session, we used our prototype which we consider of "medium fidelity" mostly focusing on the tangible aspect. We see several benefits in this approach: (1) this will allow the feedback to be focused on tangible and limit feedback on other aspect less relevant to the topic at hand. This includes potential benefits of tangible interaction, but also some limitations, which might be interesting to spot early on; (2) this will also allow to highlight important requirement regarding the integration of this new setup into the current work environment; (3) finally, this will enhance user engagement with the technology and it gives the end-users the opportunity to discuss with us on how it could be used in the future and how they see its improvement.

## 5.1 Procedure

We performed most of the sessions (24 sessions out of 26) in the control centre in charge of high-speed train in the west of France. The researcher in charge of the session (called "interviewer" in the rest of the paper) spent a full week in the centre and set up the prototype in one room. During the week, operators and managers could then come when they had time. The session were done with either one, two or three operators maximum, depending on their availability, and they lasted around 30 minutes. In total, 34 operators participated to this sessions. Each session started with a general discussion about tangible interaction and the goal of our study. Then, we performed a demonstration of our prototype. After that, we performed a semi-structured interview during which operators were allowed to test interactions, move tangible tokens and suggest new interactions. To discuss the benefits and concerns of such a system, we defined 6 categories of questions: first impression, visualisation of scenarios, use cases "How do you imagine using this tool?", opinion on the use of objects "What do you think about using objects", collaboration with other centres and considering such a tool in 10-15 years. Finally, the participants filled out a survey about their job positions and comfort with technologies. We audio (and video) recorded the sessions. In addition, we also performed two sessions with three crisis situation experts outside of the centre, following the same procedure.

## 5.2 Participants

We recruited a total of 37 participants, 13 women and 24 men. This parity is fairly representative of the parity in the operational centres. In general, the participants had a wide range of experience, 13 have been working for less than a year at their current job but 4 of them have already worked in other control centres or worked in other positions in this control centre. 6 participants have been for more than 5 years in their job. The 3 crisis situation experts are experts since 1,5 year or 3 years but have worked for at least

<footnote n="6">⁶https://toio.github.io/toio-spec/en/docs/about</footnote>

<footnote n="7">⁷https://morikatron.github.io/toio-sdk-for-unity/docs_EN/</footnote>
10 years in control centres. 25 participants considered their level of experience with technological tools to be 4 or above out 5, and 8 were familiar with tangible interaction, we asked specifically "Estimate your familiarity with tangible interactions".

## 5.3 Analysis Methodology

For the data analysis, we performed a thematic analysis following Braun and Clarke's methodology [9] in order to identify, analyse, and report themes within data. This method describes six phases to be followed before completing a thematic analysis. First, a single researcher, the interviewer, familiarised with data through the interviews' transcription done manually. Second, the same researcher started generating codes by creating 5 tables, one for each theme addressed during interviews : visualisation, use cases, technological preferences, technical limitations and general opinion. For each, we created sub-themes to code extracts of data. Third, two researchers discussed and reflected on their ideas and assumptions. They reorganised theme and sub-themes with all the data coded. Fourth, first researcher created a mind map in order to visualised the coded extracts. Fifth, the two researchers defined and names the 5 themes: (i) Actuated Tangible Tokens, (ii) Use in crisis resolution, (iii) Collaboration, (iv) Shared Visualisation, (v) Daily operation and training. Six, they wrote a first analysis.

After discussion, researchers decided to mix and reorganised the results and defined 4 themes (i) Actuated Tangible Tokens for problems solving, (ii) Collaboration, (iii) Concerns and suggestions for improvement, and (iv) Use cases. Then they rewrote the results.

# 6 Results

The findings from our interviews analysis suggest that, overall, operators identified several benefits of using actuated tokens on a shared tabletop in control centres.

## 6.1 Benefits for problem solving

**Commitment and trust.** The use of tangible tokens allows physical interaction with objects, facilitating relocation and sharing. Compared to screen visualization alone, several operators perceived our prototype table as engaging almost kinesthetically: "That's quite playful, and you take ownership of things because you can manipulate them." (P14), "There's a significant step up because you manipulate and see." (P35). They talked about trust in the system created by physical manipulation instead of being just a spectator: "Being able to manipulate, touch, it gives you more confidence in managing the issue than when you're just a spectator." (P14). One operator went further and specified "An object is much more expressive. It's really great." (P34). One operator mentioned already using pens to represent trains when dealing with a complex situation in the control room, highlight the benefits of using a tangible representation: "We can't visualise it, so we take two pens [to represent trains], and we move them on a piece of paper." (P4).

**Better representation of the network's status.** The movement of the tangible tokens was also appreciated by operators "We can see the trains moving." (P4) as it can be helpful to understand, for example, the orientation of the train when it is about to depart (P14, P23). They confirm that the use of moving tokens provides a better representation of the network's status: "That's more meaningful.

Visually, we see them moving, and we can quickly get a better idea of the situation." (P15), "It's good to see an object move, to understand well, and to visualise better." (P30). And save time: "It would be a time saver." (P7) or speed-up decision making "If it allows us to make decisions more quickly." (P2). Indeed, as identify during observations, operators waste time by searching information in documents or asking to other operators.

**Simulate multiple scenarios.** Operators appreciated the fact that it was possible to simulate multiple scenarios and display the information of each solution side by side at the same time on the screen for comparison, aiding them in decision-making: "Truly, the foundation is really excellent, having different scenarios available, being able to see them, compare them, and see how things unfold, it's great." (P8). It can help them to see a solution that they did not think about: "it contributes to decision making, to suggest things that we haven't think before" (P28). Having multiple scenarios is also important as the situation can evolve quickly and one solution might become impossible to do, requiring operators to switch to another: "We have a support to see plan A, plan B." (P14), "We're kings at changing scenarios. Situations change rapidly" (P31). For instance, in our scenario for the demonstration, the first solution is to ask the following train to rescue the blocked train. However, as long as the two trains have not arrived at the final station, operators still look for other solutions like finding another train to rescue in case it's not possible to hang both trains together.

**Keep control on the system.** Furthermore, it was important for operators to keep control on the proposed solutions, to either change something or propose a completely new one: "Having an option to take control is good. Sometimes, we mix different solutions." (P11). This highlights the importance of the acquired experience of operators, and more generally, the knowledge they have about dealing with incidents on their network which is hard to transfer to an algorithm.

## 6.2 Benefits for collaboration

In this part, we focus the use of tangible tokens on a shared display for collaboration in control centres.

**Shared tabletop.** During our interviews, 10 operators confirmed that our prototype with a shared screen would be the most useful when dealing with critical situations, confirming our initial assumption: "In a crisis situation, [a central table] would be great." (P23), "Can this interface be at the center of the centre? We place people all around it. They stand up and then return to their seats." (P36). We don't envision the operators standing around it during the entire crisis managing everything with it, but more as a display that can be used when operators need to discuss potential solutions or when one needs to get information about the alternative solutions and see which operator is doing which task.

**Brief during an incident.** Six operators mentioned that during an incident they would do a briefing with every operators in which the general manager would give an update on the situation and discuss the next steps. This briefing is mostly done with everyone at their seats nowadays, but two operators mentioned that a few years ago, the general manager would bring a map and gather everyone
around it: "The DOA [general manager] would stop everything and bring out the map. [...] Nowadays, we don't take the time to do that anymore. It used to be: stop, I explain to you what's happening, and we understand." (P23). With this new system, it could be easier to gather and brief everyone around the shared display, as you would do with a map, but with the advantages of having up-to-date information regarding the traffic on it.

**Explain impacts of different solutions.** Operators in a control room have different roles and thus a very focused vision of an incident. For instance, the operator in charge of handling the changes in the journey of passengers stuck in a stopped train will not consider the issues of the operators in charge of handling the consequence of the delay on the staff schedule of the potential switch, and thus may not understand why one solution was chosen and not another that would have less impact on the passengers' journey. Thus, seven operators mentioned that with this actuated tangible interface, it will be easier to explain the impact of the different alternative solutions to everyone "It's mainly about scenarios, what IS going to be implemented, and what CAN be implemented." (P26), especially in stressful situations during crises "Being able to explain in a tense environment is extremely challenging." (P35).

**Explain faster and only once.** Indeed, operators also have to communicate with people who might not be available when one proposes a solution: "It would allow those who didn't have enough concentration at the time it was discussed to review it, which is great." (P35), or when new operators enter the control room (because specific expertise is needed or during a shift switch): "For those who are coming in, it makes it easier for them to understand what we are doing." (P2), "It can be interesting if we want to bring people on board, for example, newcomers, to show them what happened, where we are, replay in fast forward, demonstrate what we have done, and what still needs to be done." (P14). But also to keep a trace of the chosen solution and allow everyone to see what should be done to implement it: "It will list all the tasks to be done." (P1). Additionally, according to operators, it results in time and energy savings since there is no need for repetitive explanations when the solution is readily available to all "Everything is explained, and there's no longer a need to ask questions." (P1), "It would avoid having to call out; you look when you need it, and you can reread it. Less noise than calling out." (P12).

## 6.3 Concerns and suggestions for improvement

During interviews, operators have raised concerns about the use of this device. The first one was about interest in using tangibles objects "Small objects are nice, but I don't think they're useful." (P12) or "I don't think it would help me to see moving objects." (P16). Others have been more mitigated "To see how it's going to be developed." (P8), "I don't know, I haven't had any feedback [on the use of objects]." (P7). Based on these comments, we confirm that such a tool needs further development and more scenarios need to be added to enable operators can project themselves even further ahead.

On the other side, operators raised concerns about technical problems "I'm always afraid that objects are things that disappear." (P27), "if you have an object that doesn't connect properly, they'll leave [the system] out." (P8) and their robustness. This question

was addressed by another operator, who pointed out that no matter how robust a new technology might be, it is always necessary to think about having a degraded mode. "Today we have a whole range of tools, but normally each tool has a downgraded mode: on paper, by fax, on another site." (P22). However, the aim of our device was to present tangible use cases and not to present a robust technology.

Furthermore, this new device is completely new for operators and risks to change their habits. These concerns are generally present when new systems are introduced.

## 6.4 Alternative use cases

Finally, feedback from the operators highlighted other uses for this technology.

**Collaboration with other control centres.** The opinion was quite unanimous about implementing the same tool across similar operational centres (e.g. train station control centres) "This should be implemented everywhere" (P1), "Once the scenario is determined, it's transmitted to everyone right away." (P7). However, in our interviews, it was interesting to note that while operators were ready to share their solutions with other centres, they were a bit reluctant to let people outside the room modify them by operating the tokens: "That they can view, yes, but not interact with." (P29).

**Training.** Beyond control centre use, operators recognized the tool's value for training new personnel by simulating incidents for resolution practice: "I can even see for exercises [...]. For us, indeed, training scenarios." (P5). The use of tangible objects could simplify understanding of the situation overview, especially for less-experienced operators, in visualizing its temporal evolution. Trainees could actually try to solve the same problem with another solution and encouraging their own exploration and learning process. This can be done in a collaborative context to reproduce a situation similar to a real-time crisis

# 7 Discussion

These 37 interviews provided a preliminary step towards demonstrating various aspects of tangible tokens on a shared display system. They allowed us to explore the benefits of visualising trains with tokens, comparing and visualising resolution solutions and creating solutions according to the situation. We then looked at the benefits for collaboration in the centre. For briefings, absent people, replays and information sharing, which could be more effective than they are today. The latest results emphasise the value of the tangible in improving operators' commitment, their confidence in the system and the potential of objects that can be combined or designed differently.

## 7.1 Keep operators in the loop

Our interviews support many advantages found in literature. Feelings of situation awareness improving [38], sharing data more efficient [27] and the ability to conceptualise a message [1] using tangible tokens were described by the operators during interviews. That confirm results from previous work.

As we explained in Section 3.3, real-time optimization algorithms will raise the question of keeping humans in the loop. One of the fears that generally arises is that man will no longer be useful or
able to think for himself. An operator highlight this fear "AI means fewer humans. Humans have a weight too. We know very well that with AI, the human being is just a pawn, he doesn't know anything any more." (P12).

In the vision of accomplishing better Human Machine joint effort, a few researchers underline the idea of trust. Azevedo et al. [7] and Metge et al. [50] emphasize the idea that trust leads to collaboration, which in turn leads to an understanding of the reasoning. The latter warns of a potential decline in the critical spirit of which it recommends leaving some creativity to the operator, just as Liu et al. [45] explain that allowing the human to make corrections increases satisfaction and enables better judgement of the virtual assistant's output. This notion of trust appear during our interviews: "But if we come up with a tool like this, it really has to be used for anticipation, so that we can trust all the data it contains and save time for future decisions." (P5), "Decision support, I think that's going to change a lot of things" (P6).

## 7.2 Toward techniques for collaboration

As far as the interest in collaboration is concerned, our study has shown that a system of tangible tokens on a shared display could facilitate an understanding of complex systems and supporting collaboration as in the study of Mehta et al. [48]. While collaboration between operators was central to the design of our prototype, motivating the use of a shared display and tangible tokens, our techniques of interaction were not specifically aimed at enhancing collaboration directly on the table.

Compared to our techniques, Shared feedback, proposed by Dourish and Bellotti [21] is an example of techniques focused on improving the experience of collaboration, as it consists of techniques that provide information about who the collaborators are, where the collaborators are working, and what did they do previously. Prouzeau et al. [59] highlighted the necessity of such techniques for crisis management as some of the collaboration is asynchronous (i.e. collaborators are not in the room at the same time), and stakeholders can join the crisis team late in the situation. They proposed techniques to provide group awareness information in control rooms but for a setup composed of a wall displays and several workstations. Considering the importance of communication and sharing of information in such context, confirmed by our observations and feedback sessions, it would be interesting to provide such techniques. For now, the prototype can replay a solution proposed by an operator but more information could be captured when the solution is created and displayed or when it is replayed. We could display interaction traces of the creator, or even record the audio of the time when it is created which could allow the creator to give information justifying or complementing the solutions. There are, of course, many more possibilities that should be explored involving techniques for colocated collaboration in the room but also remote collaboration between centres.

## 7.3 Limitations

As explained in the introduction of this paper, the purpose is not to provide a fully functional system, but a prototype that can be demonstrated to operators. The importance of involving them early in the design and get feedback is crucial as they can be reluctant to

use new technology that can be inadequate to their work methods. To this end, we favour the implementation of a prototype showing the use of actuated tangible interaction on a shared display but with limited functionality. This might have impacted the feedback we received in our sessions and should be taken into consideration. However, the lesson learnt during our feedback sessions will allow us to continue our implementation and provide a more complete prototype that we will be able to evaluate.

It is also important to take into account that we conducted our user tests in a single operational centre for high-speed train. We made this choice because our on-site visits suggest such centre have to manage incidents with an impact that can span to a large part of the country compared to control centre managing smaller lines, and thus are more interesting for our use-case. However, we believe that our system would also be usable in other control centres, as the work gestures are generally the same. Furthermore, interviews with three experts who are not from this centre confirmed that other centres would be interested in collaborating with us on the development of an actuated tangible interaction device for crisis management.

Finally, it would have been interesting to compare our proposed system with current tools in railway control centres; however, this is not possible for two main reasons. Firstly, the integration of digital tabletops with actuated tangible tokens, focusing only on crisis management represents a fundamentally different interaction paradigm, which may not have direct counterparts in existing systems. Secondly, there are no existing systems that proposes solutions to solve incidents. This lack of comparable systems makes it difficult to perform a fair and meaningful comparison. Consequently, we focused on evaluating the advantages and acceptability of our proposed system through direct feedback from operators.

## 7.4 Generalisation of this work

Our research centered on crisis management tools for railway control centres. The feedback we have received from operators regarding the use of a shared table with actuated tangible tokens appears to be promising for future advancements. It is now important to explore its scalability. Although the size of our current prototype allows only 4 or 5 people at the same time, it is crucial to explore how the use of tangible tokens on a tabletop would work in larger collaborative environments, such as control centers, with up to 15 or 20 participants, as described in Section 3. Furthermore, it is important to explore how to manage a large number of tokens, in case, for instance, of large events involving a high number of trains.

Our insights on the use of actuated tangible tokens on a shared tabletop is, however, not limited to railway control centres and could be applied to various other domains. First, our tool could be applied to other types of control centres to assist in monitoring their systems and provide a shared representation for all operators during crises. This shared representation could facilitate spatio-temporal data analysis, enabling, for instance, operators to understand the near or distant future consequences of decisions made in specific geographical areas and explore diverse solutions to solve the crisis, as shown in road traffic management by Prouzeau et al. [57].
Furthermore, our prototype could serve as an initial step that can
inspire new ideas for exploring large spatiotemporal datasets be-
yond control rooms or railway management. For instance, it could
potentially be adapted for use in urban planning to visualise and in-
teract with data on city growth, traffic patterns, and environmental
changes over time. The system would enable planners to compare
different development scenarios and optimise urban layouts effec-
tively [47]. Additionally, this prototype could inspire applications
in fields like supply chain management, where it might help users
explore various optimisation algorithms by adjusting parameters
interactively to identify the most efficient logistics routes [44].

8 Conclusion

In this paper, we tackled the challenges of collaboration, informa-
tion sharing and decision making in railway control centres. To
address these, we developed a prototype of actuated tangible in-
teractions on a tabletop. We conducted qualitative study with 37
operators and our results suggest that such a technology could help
operators during crises for information sharing, problem solving
and collaboration. In the future, it would be interesting to assess
the performance of operators when dealing with incidents using
a more advanced version of our prototype. During such study, it
would be also interesting to investigate the use of the setup and
how it correlates with some cognitive measure, like the mental
workload, to deepen our understanding of the impact of tangible
interactions.

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