# An Overview of Shared Mobility Operational Models in Europe
## 2 Materials and Methods  
For the purposes of this review, Web of Science (WoS), Elsevier, and Academia were used as the primary databases for literature research, as they encompass several key scientific resources, including the Science Citation Index Expanded, Scopus, Urban Transportation, Urban Mobility, Transportation Research Record, and Transportation Science Technology.  
During the database searches, a range of keywords was applied to narrow and focus the results. For each modality, a primary keyword was used along with its various iterations to maximize the comprehensiveness of the search. The keywords included \"carsharing\", \"car sharing\", \"bikesharing\", \"bike-sharing\", \"bike sharing\", \"scooter sharing\", \"e-scooter sharing\", and \"electric scooter sharing\". Although the terms are conceptually similar, different authors often use varying terminology; therefore, all potential variations were incorporated to ensure the breadth and inclusivity of the search. As carsharing was the central focus of the review, particular attention was given to this area, with an emphasis on fleet optimization and related research.  
From the numerous scientific papers and journal articles retrieved, only open access publications were selected, with the search restricted to those published after 2010. This criterion was applied due to the rapid evolution of technology in the field of shared mobility, rendering older studies less relevant to the current state of the field.  
In accordance with the defined criteria, the subsequent step involved systematic screening of paper titles. Given the substantial number of publications identified during the initial search, comprehensive title screening was conducted. Papers whose titles corresponded to the research focus were selected for full-text retrieval. The abstracts of the selected papers were then reviewed to further exclude those that did not meet the inclusion criteria. The reference lists of the selected papers were examined. If any cited works were deemed relevant and academically valuable, they were included as supplementary sources, irrespective of their publication date prior to 2010. The overall selection process is illustrated in Figure 1.  
There are some research limitations associated with this paper. All the literature considered and reviewed was in English, which raises the possibility that closely related articles written in other languages were not included. Additionally, only open access articles were reviewed, which further limited the scope of the available literature.  
\begin{table}
\begin{tabular}{p{142.3 pt} p{284.5 pt}} \hline \hline
**Term** & **Definition** \\ \hline Station-based & A shared mobility model where vehicles are picked up and returned at predefined physical locations (stations). These can function either as one-way (different pick-up and drop-off stations) or round-trip systems (same pick-up and return location). \\ \hline Dock-based & A subtype of a station-based system in which vehicles must be physically secured to docks or posts. Common in third-generation bikesharing systems, this model ensures controlled access and reduced theft. \\ \hline Free-floating & A model allowing users to pick-up and drop-off vehicles anywhere within a designated service area, without the need for fixed stations. Offers maximum flexibility and is commonly used in carsharing and e-scooter services. \\ \hline Dockless & A system without physical docks, allowing vehicles to be left in flexible locations. However, if vehicles must be returned to marked or geofenced zones, the system leans toward being station-based in practice. \\ \hline Peer-to-peer (P2P) & A model where private individuals rent out their own vehicles via a third-party platform. The operator does not own the fleet but facilitates transactions and usage between users. \\ \hline \hline \end{tabular}
\end{table}
Table 1: Glossary of key terms in shared mobility models.