## 3 Study Area and Data
### Research Data Acquisition and Processing
#### 3.2.1 Road Data Acquisition and Processing  
The road network map of the Kowloon area of Hong Kong obtained from the OpenStreetMap ([[https://openmaptiles.org/](https://openmaptiles.org/)]([https://openmaptiles.org/](https://openmaptiles.org/)); Access Date: 1 December 2023) website contains geographic information about the roads, streets, highways, bridges, tunnels, sidewalks, \begin{table}
\begin{tabular}{c c} \hline \hline
**District** & **Number of Traffic Accidents** \\ \hline Wong Tai Sin District & 1330 \\ \hline Kowloon City District & 2158 \\ \hline Kwun Tong District & 2402 \\ \hline Sham Shui Po District & 1766 \\ \hline Yau Tsim Mong District & 2736 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Number of traffic accidents distributed in various districts of Kowloon Peninsula. Figure 1: Illustration of the administrative divisions of the Kowloon Peninsula of Hong Kong. and other transportation facilities and buildings in the area. The obtained road network of the Kowloon Peninsula area of Hong Kong is shown in Figure 2.  
The obtained road network attributes of the Kowloon Peninsula of Hong Kong are shown in Table 3.  
The value of the \"lanes\" attribute indicates the number of lanes in the road, including all lanes in a two-way road. For example, a two-way road with two lanes can be labeled as \"lanes = 4\", where two lanes are used in each direction. The value of the \"shape\" attribute indicates the shape of the line elements; in this study, the road network is folded lines. The value of the \"highway\" attribute indicates the class and type of the road, and there are mainly the following categories:  
1. Motorway: highway;
2. Trunk: trunk highway;
3. Primary: major roads;
4. Secondary: secondary roads;
5. Tertiary: third-class roads;
6. Residential: residential roads;
7. Unclassified: unclassified roads. The contents of the road network data attribute table are shown in Table 4. \begin{table}
\begin{tabular}{c c} \hline \hline
**Property Name** & **Hidden Meaning** \\ \hline fid & The “fid” can be used to uniquely identify an element on the map. \\ \hline shape & The “shape” attribute is usually used to indicate the shape of a line element. \\ \hline length & The “length” attribute is usually used to indicate the length of a road line element. \\ \hline highway & The “highway” attribute is usually used to indicate the type of road. \\ \hline lanes & The “lanes” attribute is usually used to indicate the number of lanes in a roadway. \\ \hline name & The “name” attribute is usually used to identify the name of a location. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: OpenStreetMap road network attributes. Figure 2: Road network map of Kowloon Peninsula, Hong Kong. OpenStreetMap data are contributed by community volunteers, so there may be an incomplete coverage of the map data, and at the same time, according to the research objectives of this paper, it is also necessary to carry out a secondary processing of the road network, so as to ensure that the adopted road network can be used to carry out the research on the identification of traffic black spots at road intersections. The process of secondary processing of the road network mainly includes the following steps:  
Road network connectivity processing: in some cases, the road network may have the problem of discontinuity, that is, some areas cannot be reached or can only be reached through longer paths, which will affect the recognition results of traffic black spots, so it is necessary to carry out connectivity processing. Road network segmentation: road network segmentation consists in cutting the road network into small segments, which can be nodes, edges, or regions, which can improve the computational efficiency and accuracy of the traffic black spot recognition algorithm. In this study, the road network segmentation is performed at road network intersections. Remove redundant road network lines. Turn two-way roads into unidirectional lines, circular intersections into unidirectional cross-connection-type lines, etc.