## 5 Method Design
### Trajectory Similarity Search
#### 5.3.3 Filtering Strategy
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Condition**} & \multirow{2}{*}{**Method**} & **\# of Input** & **n: \# of Involved** & **k: \# of Output** & **Reduction** & **Time (ms)** \\  & & **(Trajectory/Point)** & **(Trajectory/Point)** & **(Trajectory)** & **(k/n)** & **Time (ms)** \\ \hline L64, threshold = 0.8 & PPJion+ & 6,958,984 & 6,958,984 & 1 & \textgreater{}99.99\% & 1614 \\  & PMMTss & 6,958,984 & 65,130 & 1 & \textgreater{}99.99\% & 65 (14 + 51) \\ \hline L32, threshold = 0.8 & PPJion+ & 6,958,984 & 6,958,984 & 1 & \textgreater{}99.99\% & 1295 \\  & PMMTss & 6,958,984 & 65,130 & 1 & \textgreater{}99.99\% & 16 (8 + 8) \\ \hline L16, threshold = 0.8 & PPJion+ & 6,958,984 & 6,958,984 & 2 & \textgreater{}99.99\% & 5792 \\  & PMMTss & 6,958,984 & 65,130 & 2 & \textgreater{}99.96\% & 8 (5 + 3) \\ \hline L8, threshold = 0.8 & PPJion+ & 6,958,984 & 6,958,984 & 3 & \textgreater{}99.99\% & 2091 \\  & PMMTss & 6,958,984 & 65,130 & 3 & \textgreater{}99.94\% & 8 (6 + 2) \\ \hline L4, threshold = 0.8 & PPJion+ & 6,958,984 & 6,958,984 & 2 & \textgreater{}99.99\% & 1959 \\  & PMMTss & 6,958,984 & 65,130 & 2 & \textgreater{}99.93\% & 7 (6 + 1) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Running time and workload reduction of PPJion+ and PMMTss for sample dataset. Figure 7: Time-consuming ratio of data extraction and trajectory search in PMMTss. by 99.7%, 98.8%, and 97.6%, respectively. Moreover, our solution presents higher filtering efficiency, lower deployment cost, and a flexible search interface. Although our solution has achieved good results, there are still some limitations. For example, we do not consider the route within the metro network when we measure the similarity between two different trajectories. It is a very important factor, which could affect the accuracy of trajectory similarity search. Thus, we plan to address this limitation in our future work, so that we can adopt an RNN-based model [27] or a data fusion method [7] to infer the route choices for passengers. ## 8 Patents

[PERSON], [PERSON], and [PERSON]. A Parallel Multi-way Merging-based Trajectory Similarity Search for Metro Passengers [P]. Yunnan Province: CN115344795 AB.2022-12-09. The invention patent has been granted. Conceptualization, W.H. and W.X. ; methodology, W.H. and W.X. ; software, W.H. ; validation, W.H. ; investigation, W.X. ; writing--original draft preparation, W.H. and W.X. ; writing--review and editing, W.H., W.X. and X.W. ; visualization, W.H. and W.X. All authors have read and agreed to the published version of the manuscript. This research was funded by the National Natural Science Foundation of China (NSFC) [Number: 61862066]. Not applicable. The data presented in this study are available on request from the corresponding author. The authors declare no conflict of interest. ## References

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