## 3 Research Methodology
### Material Collection  
In this subsection, the research questions, inclusion criteria, exclusion criteria, and the PRISMA four-phase flow diagram are discussed. The study at hand undertakes a systematic review of the literature to address the following research questions:  
1. What would be the classification of the SMP based on problem types, variants, and characteristics? 2. What are the solution approaches that have been employed to solve the SMP? 3. What are the current trends of the SMP? 4. What are the challenges and future work direction in the routing and matching optimisation of SMP? The first stage is to plan on developing the research aim and questions, keywords, and a set of inclusion and exclusion criteria. The research aim was framed to identify the related studies of SMP based on the types, variants, characteristics, and solution approaches. Thus, (\"ridesharing\" OR \"ridesplitting\" OR \"ridepooling\" OR \"taxisharing\" OR \"shared taxi\" OR \"carpooling\" OR \"buspooling\" OR \"vanopooling\" OR \"multi-modal\") AND (\"ride\" AND \"matching\") were chosen to be the search keywords. As mentioned in [3], ridesharing, ridesplitting, ridepooling, taxisharing, shared taxi, carpooling, busyooling, vanpooling, and multi-modal are types of problems under the SMP. The (\"ride\" AND \"matching\") search term was used in the database search to ensure that the search is focused on the subject area of mathematics and computer science-related fields, especially for the model formulation, instead of social sciences-related studies in shared mobility. Based on the PRISMA guidelines, a total of 12 abstract and citation databases (ACM Digital Library, Emerald Insight, IEEE Xplore, INFORMS, MDPI, PLOS One, SAGE, ScienceDirect, Scopus, Springer Link, Taylor & Francis Online, and Wiley Online Library) were \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Paper** & **Highlights** & **Year** & **Number of Papers** \\ \hline
[4] & Challenges in economic, social, institutional, and technological aspects. & & \\  & Benefits and drawbacks of dynamic ridesharing. & 1974–2010 & 12 \\  & Future direction of dynamic ridesharing. & & & \\ \hline
[5] & Characteristics of dynamic ridesharing, rideshare variants, and multi-modal & 1977 – 2012 & 38 \\  & ridesharing problem. & & & \\ \hline
[2] & Explored the history of ridesharing in North America for five key phases. & 1942–2011 & 43 \\ \hline
[1] & Detailed classification of the ridesharing system and matching agencies. & 1961–2013 & 52 \\ \hline
[6] & Discussed the evolution of dynamic ridesharing from the past and present to its future with information and communication changes. & 1977–2011 & 19 \\ \hline
[7] & Reviewed P2P ridesharing variants literature with solution algorithms. & 2004–2020 & 42 \\  & Future direction is discussed. & & & \\ \hline
[8] & Reviewed carsharing, ridesharing and carpooling with solution algorithms. & 2008–2019 & 86 \\  & Challenges and opportunities of ridesharing. & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Related Review Papers. searched for peer-reviewed papers by keywords contained in the title, abstract, and the main body of the papers. The last search was performed in January 2021, and we restricted the search to all literature published from January 2010 till January 2021. In Figure 1, the search results are presented in a flowchart. The search firstly resulted in 1319 records overall. After removing the books, chapters, editorials, reports, and articles that are not in the English language, the search records were reduced to 1094. Then, the total number of articles was further reduced to 460 articles after evaluating the title and abstracts related to the inclusion and exclusion criteria.