## 3 Review of Studies Related to MaaS in the Context of Multi-
### Summary of Studies  
The term \"MaaS\" in conjunction with \"multi-modal\" provides a clue for narrowing down the number of papers relevant to both \"MaaS\" and \"multi-modal\". The query string we used to search the first category of papers is AB = (\"MaaS\" AND \"multi-modal\"), which is aimed to find the papers with keywords \"MaaS\" and \"multi-modal\" in the abstract. The search returned 18 results from the Web of Science Core Collection. Figure 4 shows the distribution of these papers published over the years. After content analysis, 17 papers are retained. These papers were published during the years between 2017 and 2025. Five papers were published during the years between 2017 and 2020 and 12 papers were published during the years between 2021 and 2024. The number of published papers increases during the years from 2021 to 2023. Based on the above information, papers with the keywords \"MaaS\" and \"multi-modal\" in the abstract might provide a clue for identifying potential emerging research directions. The research questions addressed in the papers found by the refined search of this section are summarized in Table 4. \begin{table}
\begin{tabular}{c l} \hline \hline
**Paper** & **Research Questions** \\ \hline
[46] & What are the challenges and opportunities of sustainable mobility in post-COVID-19 period? \\ \hline
[47] & Is MaaS able to address the challenges of mothers in multi-modal mobility? \\ \hline
[65] & How to develop a general modelling framework for MaaS based on analysis of the relevant literature considering main actors and factors? \\ \hline
[97] & What are the requirements of MaaS? How to develop a sustainable business model for transport operators at varying levels of MaaS considering risk and data sharing? \\ \hline
[48] & Who and why users took part in the trial of a MaaS service? Whether the trial experience satisfied the users’ motives? \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Summary of research questions addressed in the papers published between 2017 and 2024 in the Web of Science Core Collection with keywords “MaaS” and “multi-modal” in the abstract. \begin{table}
\begin{tabular}{c c} \hline \hline
**Topic** & **Papers** \\ \hline Impact & [84] (2022), [85] (2017), [86] (2024), [87] (2023), [88] (2023), [89] (2023), [90] \\  & (2022), [91] (2021), [92] (2018), [93] (2023), [94] (2021), [95] (202 \begin{table}
\begin{tabular}{c p{341.4 pt}} \hline \hline
**Paper** & **Research Questions** \\ \hline
[84] & How MaaS could impact GHG emissions in an urban setting? \\ \hline
[66] & How to simulate multi-modal operations of Mobility as a Service in low-density cities? \\ \hline
[49] & 1. To what extent can the MaaS promises to people and government be delivered? Could any unanticipated societal issues arise from adoption of MaaS?2. What are the challenges for urban governance from potential MaaS adoption, and the recommended responses to these challenges? \\ \hline
[50] & Are there principles for sustainable Mobility as a Service? Can we identify principles for sustainable MaaS in areas with high car dependency? \\ \hline
[51] & How does MaaS influence commuting mode choice of commuters? \\ \hline
[98] & How to implement multi-modal shared mobility through policy implementation? \\ \hline
[99] & What is the planning process for implementing MaaS? \\ \hline
[100] & How to develop an architecture for MaaS to tackle the potential threats? \\ \hline
[85] & Whether the way bus services might be offered will be changed under MaaS? \\ \hline
[67] & How to design a mobility hub to achieve sustainability, performance and efficiency by reducing vehicle miles in the city and combining many multi-modal transport options for transferring passengers? \\ \hline
[86] & How about the competitiveness of MaaS multi -modal travel options with respect to private car usage? \\ \hline
[68] & How to determine the route choices of different transport modes that can jointly form a complete path for transporting the user from origin to destination? \\ \hline \hline \end{tabular}
\end{table}