## 2 Previous Review Paper  
A number of review or survey papers discuss ridesharing from different scopes and perspectives. The authors of [4] defined real-time or dynamic ridesharing and discussed the challenges of dynamic ridesharing based on economic, social, institutional, and technological aspects. The possible benefits and drawbacks of dynamic ridesharing are explored in detail in comparison with traditional ridesharing. Then there is [5] which focused on the review of optimisation for dynamic ridesharing. The discussion included the aspect of features, overall objectives, variants, as well as the challenges in developing the ridesharing system.  
Additionally, the authors of [2] explored the past, present, and future of ridesharing in North America. First, the history of the ridesharing system is discussed in five different phases from 1942 till 2012. This is followed by a discussion of the existing ridesharing system. The future directions of the ridesharing system are also suggested.  
The authors of [1] classified the ridesharing matching agencies that are accessible online based on target markets, primary search criterion, classes, business functions, and service types. They stated the challenges of designing the ridesharing system, including elements of pricing, high-dimensional matching, trust and reputation, and institutional design. A future challenge for desirable services of matching agencies is suggested in the paper. Still focusing on IT advancements, ref. [6] presented a chronology of the transformation of dynamic ridesharing from early operator-based to real-time database-driven ridesharing services through the changes in Information and Communication Technologies (ICTs) over the last two decades. They claimed that the interaction between dynamic ridesharing and ICTs will continue to evolve until a balance is achieved.  
More recently, ref. [7] performed a review study that mainly focuses on different problem variants of P2P ridesharing with the solution approaches. Their paper consists of a general literature review with 42 papers discussed. However, the paper does not mention the specific databases and techniques that are used in selecting the papers. In terms of the classification of problem variants, ref. [7] discussed solely the number of riders and drivers. In this study, two different types of problem variant classifications are identified and discussed: (i) the number of riders and drivers, and (ii) the number of origins and destinations.  
Similarly, ref. [8] conducted a review of optimisation problems related to ridesharing, carsharing, and carpooling, together with the employed methodologies used to solve these problems. The methodologies include exact, approximate, and simulation methods. The challenges for ridesharing and carpooling in solving large-scale problems are identified, such as the concept of 'agile' optimisation. A total of 86 papers are selected, from 2008 to 2019, sourced from the Web of Science (WoS) database. The researchers in [8] make use of the term \"carsharing\" to represent both \"ridesharing\" and \"carpooling\" in conducting the review. However, \"carsharing\" is one part of the shared mobility that is mentioned in [9], which reduced the number of vehicle ownership by sharing the vehicles among people, such as in neighborhood carsharing. In this study, we only focus on the sharing of rides or the so-called pooling (instead of sharing) of vehicles. As compared to [8], this paper studies more in-depth the shared mobility based on characteristics, problem variants, and solution approaches.  
In general, the aforementioned review papers only surveyed a moderate number of papers and did not explicitly present the methodology of their review. Instead, they mainly focused on the findings. These papers are presented in Table 1, highlighting the focus of their research. They are categorised according to the year of publication and number of papers reviewed.