## 3 Bus Network Model  
The network model should meet requirements in terms of identifying the influence range of line adjustments, the path calculations, the route selections, and so on. One can assume that the line adjustment will only affect passengers on the 'associated' lines, including logical and spatial related lines, so the key to designing a bus network model is to reflect the spatial and logical relationship (such as subordination and transfer) between different stops, as well as the relationship between stops and lines. The bus sub-network model can be defined as the integration of stops, routes, and transfer information with all lines that intersect or overlap with the adjusted lines. Classified by elements, this model can be divided into a sub-stop model, route model, transfer model, and various other levels, as shown below in Figure 2.  
1. The sub-stop model is the smallest unit in a bus network and is used to describe a single line and unidirectional stop. It is also the core model of the entire network model. Its elements include the line that the stop belongs to, the direction (up/down), name, ID, stop order, distance and travel time from the previous stop, latitude and longitude, adjacent sub-stop collection (which refers to the stops set that can be reached by walking), and stop class (which is divided into four classes: Class1, directly adjusted stops; Class2: walkable stops from direct stops; Class3: stops on the same line as direct stops; Class4: other associated stops). The sub-stop ID is unique, which means that different bus lines have different IDs when they pass through bus stops with the same physical properties.
2. The route model is used to describe the information about stops upstream and downstream. Such information mainly includes the route name, route ID, collection of upstream and downstream stops, the collection of transfers of each stop (adjacent sub-stops), and the starting and ending overlap stop order between the current line and the adjusted line. The route model is used to calculate the association of the stops on the same lines.
3. The transfer model focuses on transfer stop and route information, expressing the relationships between different lines. It records details about the upstream and downstream transfers, the starting and target transfer stops, riding distance before and after the transfer, walking distance during the transfer, and the transfer stop itself.  
To automatically identify the impact range of route adjustments, the process begins with obtaining the location information of the stop to be adjusted. Using information such  
Figure 2: Bus network model.  
as stop location, route, and walking distance, the system can identify 'directly related' (i.e., adjacent, same line) routes and stops. Then, the 'indirectly related' stops and routes are identified by utilizing 'directly related' stop information, route data, and transfer details. Together, these directly and indirectly related stops and routes form a bus sub-network. Among these factors, 'walking distance' is a key parameter that controls the number of'related' stops and routes, making it one of the most important variables in defining the size of the bus sub-network and optimizing the model's computational efficiency.