## 2 Methodology
### Vehicle Path Feature Extraction
#### 2.4.3 Vehicle Path Identification and Feature Extraction  
The core concepts of vehicle path feature extraction are refined into a workflow to present the analysis process more intuitively and clearly. The routeInferMain() function serves as the main function for vehicle path feature extraction, containing multiple sub-functions. The input and output parameters of this main function are described in Tables 1 and 2.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Parameter Category** & **Parameter Name** & **Type** & **Input Function** & **Output Function** & **Description** \\ \hline \multirow{6}{*}{Input Parameters} & gon\_radius & double & makePolygon2; routeDiagnose & - & Circumscribed circle radius of the regular polygon representing node entry/exit range (referred to as node regular polygon) \\ \cline{2-6}  & gon\_nvert & double & makePolygon2 & - & Number of vertices (i.e., sides) of the node regular polygon \\ \cline{2-6}  & trsi & table & plotRoad; nodeDigger & - & Trajectory data \\ \cline{2-6}  & inter\_origin & table & makePolygon2; plotRoad; routeInfer & - & Node data \\ \cline{2-6}  & vinfo & table & routeInfer & - & Vehicle basic feature data \\ \cline{2-6}  & figurepath & char & - & - & Parent path for image storage \\ \cline{2-6}  & route\_dialog & Empty matrix or table & routeDiagnose & - & Abnormal path vehicle statistical data \\ \hline \multirow{6}{*}{Temporary Parameters} & gonxy & cell & nodeDigger & makePolygon2 & Vertex coordinants of all node regular polygons \\ \cline{2-6}  & roadfig & figure & - & plotRoad & Visualization of nodes and node regular polygons \\ \cline{2-6}  & node & double & routeInfer & nodeDigger & Index of nodes to which vehicle trajectory points belong \\ \cline{2-6}  & route2 & table & routeDiagnose & routeInfer & Vehicle path data (without '00' nodes, adjacent nodes not merged for individual vehicles) \\ \cline{2-6}  & route3 & table & routeDiagnose & routeInfer & Vehicle path data (without '00' nodes, adjacent nodes merged as strings and vectors for individual vehicles) \\ \cline{2-6}  & route\_dialog\_0 & table & - & routeDiagnose & Vehicle path data passing through 0 nodes \\ \cline{2-6}  & route\_dialog\_1 & table & - & routeDiagnose & Vehicle path data passing through 1 node \\ \hline \multirow{6}{*}{Output Parameters} & route\_dialog\_out & table & - & routeDiagnose & Statistics of vehicles passing through 0 and 1 nodes \\ \cline{2-6}  & route\_struct & struct & - & - & Final output of vehicle path data, containing gon,radius, gon,nvert, roadfig, node, route2, route3, route\_dialog\_0, route\_dialog\_1, gonxy \\ \cline{1-1} \cline{2-6}  & route\_dialog\_1 & - & routeDiagnose & Vehicle path data passing through 0 nodes \\ \cline{1-1} \cline{2-6}  & route\_dialog\_1 & - & routeDiagnose & Vehicle path data passing through 1 node \\ \hline \multirow{6}{*}{Output Parameters} & route\_dialog\_out & table & - & routeDiagnose & Statistics of vehicles passing through 0 and 1 nodes \\ \cline{1-1} \cline{2-6}  & route\_struct & struct & - & - & Final output of vehicle path data, containing gon,radius, gon,nvert, roadfig, node, route2, route3, route\_dialog\_0, route\_dialog\_1, gonxy \\ \cline{1-1} \cline{2-6}  & route\_dialog\_0 & - & routeDiagnose & Vehicle path data passing through 0 nodes \\ \cline{1-1} \cline{2-6}  & route\_dialog\_1 & - & routeDiagnose & Vehicle path data passing through 1 node \\ \cline{1-1} \cline{2-6}  & route\_dialog\_out & - & routeDiagnose & Statistics of vehicles passing through 0 and 1 nodes \\ \cline{1-1} \cline{2-6}  & route\_struct & struct & - & - & Final output of vehicle path data, containing gon,radius, gon,nvert, roadfig, node, route2, route3, route\_dialog\_0, route\_dialog\_1, gonxy \\ \hline \hline \end{tabular}
\end{table}
Table 1: Parameter information and sub-function relationships of the main vehicle path feature extraction function routeInferMain().