# Estimation of Driving Direction of Traffic Accident Vehicles for Improving Traffic Safety
## 4 Experimental Results
### Visualization  
This section discusses the visualization of AD-specific directional information on the map at the villages/towns/neighborhoods level. First, we define each AD's center \begin{table}
\begin{tabular}{l c c c} \hline \hline \multirow{2}{*}{**Administrative District**} & \multirow{2}{*}{**Dimension (km2)**} & \multicolumn{2}{c}{**Traffic Accidents**} \\ \cline{3-4}  & & **Number** & **TAR** \\ \hline Cheonan-si & 636.14 & 3039 & 4.7773 \\ Gongju-si & 864.19 & 461 & 0.5334 \\ Boryeong-si & 573.78 & 424 & 0.7390 \\ Asan-si & 542.19 & 1185 & 2.1856 \\ Seosan-si & 741.29 & 667 & 0.8998 \\ Nonsan-si & 554.75 & 350 & 0.6309 \\ Gyveryong-si & 60.72 & 56 & 0.9223 \\ Dangjin-si & 704.26 & 690 & 0.9798 \\ Geumsan-gun & 577.13 & 111 & 0.1923 \\ Buyeo-gun & 624.52 & 193 & 0.3090 \\ Seocheon-gun & 365.70 & 256 & 0.7000 \\ Cheongyang-gun & 479.10 & 151 & 0.3152 \\ Hongseong-gun & 443.99 & 244 & 0.5496 \\ Yesan-gun & 542.62 & 326 & 0.6008 \\ Taean-gun & 515.79 & 270 & 0.5235 \\ \hline Chungcheongnam-do & 8226.17 & 8423 & 1.0239 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Statistics of traffic accidents by AD (city/gun) in Chungcheongnam-do received by the police as of 2021.  
coordinates \((\bar{x}_{AD},\bar{y}_{AD})\) for visualization. Then, we created a lookup table containing the center coordinates of 207 ADs at the village/town/neighborhood level using Kakao Maps API's reverse geocoding. Second, we matched all accident locations \((x_{acc},y_{acc})\) to their corresponding text addresses using geocoding and then matched them to the lookup table. During this process, we accumulated the frequency of Northbound and Southbound directions for each \((\bar{x}_{AD},\bar{y}_{AD})\) (Figure 5). Figure 6 shows the results of mapping the frequency of Northbound and Southbound directions for each \((\bar{x}_{AD},\bar{y}_{AD})\) on the map. In the visualization, the direction with a higher frequency is displayed. The green upward arrow, red downward arrow, and black bidirectional arrow represent Southbound, Northbound, and no-priority directions, respectively. In addition, a tooltip is used to indicate the cursor's position explicitly. Table 3 summarizes the number of traffic accidents by city/county in Chungcheongnam-do as of 2021. Since villages/towns/neighborhoods have a minimum unit size and contain much information, we aggregated the data by city/county. Southbound traffic accidents represented 57.25% of the total cases, about 14.5% higher than Northbound. Northbound  
Figure 5: Example of histogram on map. Figure 6: The estimated representative accident directions by dong/eup/myeon based on frequency within the Chungcheongnam-do (green upward arrow: priority given to Northbound direction, red downward arrow: priority given to Southbound direction, black bidirectional arrow: no priority direction). was higher only in 'Cheonan-si' and 'Geumsan-gun', with 6.02% and 0.82% higher Northbound ratios, respectively. The remaining 13 ADs all had a higher proportion of Southbound traffic accidents. In order of decreasing Southbound ratio, they were 'Yesan-gun', 'Cheongyang-gun', 'Seosan-si', 'Hongseong-gun', 'Seocheon-gun', 'Nonsan-si', 'Gongju-si', 'Boryeong-si', 'Buyeo-gun', 'Gyeryong-si', 'Asan-si', 'Dangjin-si', and 'Taean-gun', with a difference of about 9.84% to 71.42% higher Southbound ratios. However, the AD with the highest difference in Northbound and Southbound ratios, 'Taean-gun', had minimal traffic accidents and thus low reliability. Excluding this AD, the difference in Northbound and Southbound ratios is approximately 9.84% and 26.66%, respectively. Furthermore, 'Taean-gun', 'Cheonan-si', and 'Dangjin-si' have a significant difference between the number of traffic accidents in Table 2 and the number of traffic accidents in Table 3, indicating that much data were lost due to inaccurate driving direction information in the incident reports.