## 6 Discussion
### Result of Threshold Calculation
#### 6.2.3 Roadside Fixed Object Variable  
Table 7 shows the threshold calculation results for the variables related to fixed objects. The total CoO of the variable of horizontal distance between the road and the fixed object was 7.3, indicating the largest impact, followed by the fixed object density variable with a CoO value of 5.8. In the sections where the horizontal distance between the road and the fixed object was less than 3 m, the probability of a fatal accident was high, especially when the fixed object was installed at a distance than 1.5 m; there was a sharp increase in the probability of a serious accident. Even when the horizontal distance between the road and the fixed object was 3-5 m, the probability of a slight accident and a fatal accident was high, but the distribution of severity varied depending on the type of the fixed object. The values in the results of the existing research are similar to those with the range of recovery distance (the width at which the roadway departure of a vehicle can be recovered) at 3 to 4.6 m [52]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Category** & & **Slight** & **Serious** & **Fatal** \\ \hline \multirow{2}{*}{Compound curve} & Y & \(-20.2\) & \(20.7\) & \(2.1\) \\  & N & \(7.7\) & \(-7.1\) & \(-0.3\) \\ \hline Total & & \(-12.5\) & \(13.6\) & \(1.9\) \\ \hline Average (class = 6) & & \multicolumn{3}{c}{\((-12.5+13.6+1.9)/6=0.5\)} \\ \hline \multirow{2}{*}{Reverse curve} & Y & \(1.8\) & \(21.5\) & \(-14.5\) \\  & N & \(-0.1\) & \(-1.2\) & \(1.4\) \\ \hline Total & & \(1.7\) & \(20.3\) & \(-13.1\) \\ \hline Average (class = 6) & & \multicolumn{3}{c}{\((1.7+20.3-13.1)/6=1.5\)} \\ \hline \multirow{2}{*}{Continuous curve} & Y & \(1.9\) & \(22.4\) & \(-14.9\) \\  & N & \(-0.1\) & \(-0.5\) & \(0.6\) \\ \hline Total & & \(1.9\) & \(21.9\) & \(-14.4\) \\ \hline Average (class = 6) & & \multicolumn{3}{c}{\((1.9+21.9-14.4)/6=1.6\)} \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Results of curve type of road variable threshold calculation. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Category** & & **Slight** & **Serious** & **Fatal** \\ \hline \multirow{2}{*}{Distance between the roadway and the fixed object} & \(<\)3 m & \(-1.1\) & \(-71.1\) & \(112.1\) \\  & 3–5 m & \(14.7\) & \(-23.3\) & \(11.3\) \\  & \(\geq\)5 m & \(-6.7\) & \(64.3\) & \(-34.3\) \\ \hline Total & & \(7.0\) & \(-30.1\) & \(89.1\) \\ \hline Average (class = 6) & & \multicolumn{3}{c}{\((7.0-30.1+89.1)/9=7.3\)} \\  & N \(>2\) & \(-53.2\) & \(2.2\) & \(75.6\) \\ Density of fixed objects & \(1<N\leq 2\) & \(-7.7\) & \(-11.7\) & \(21.6\) \\  & N \(\leq 1\) & \(38.8\) & \(23.2\) & \(-36.9\) \\ \hline Total & & \(-22.0\) & \(13.7\) & \(60.3\) \\ \hline Average (class = 6) & & \multicolumn{3}{c}{\((-22.0+13.7+60.3)/9=5.8\)} \\  & Streetlight & \(-0.4\) & \(4.0\) & \(-3.1\) \\  & Pier & \(-0.3\) & \(0.5\) & \(-0.2\) \\ Type of fixed objects & Traffic light & \(-0.3\) & \(1.0\) & \(-0.6\) \\  & Utility pole & \(0.1\) & \(-3.6\) & \(4.0\) \\  & Road sign & \(0.2\) & \(1.6\) & \(-1.7\) \\  & Tree & \(0.3\) & \(0.2\) & \(-0.5\) \\ \hline Total & & \(-0.9\) & \(1.9\) & \(0.0\) \\ \hline Average (class = 18) & & \multicolumn{3}{c}{\((-0.9+1.9-0.0)/18=0.1\)} \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Results of the roadside fixed object variable threshold calculation. When the horizontal distance between the road and the fixed object and the type of fixed object in the crash were considered together, the results showed that the probability of a fatal accident greatly increased when utility poles were installed at a distance of less than 3 m. The New York State Department of Transportation (NYSDOT) recommends installing utility poles inside rather than outside of the curved road, and recommends that utility poles installed close to the road should be at a distance of 3 m or more from the outer edge of the road [53].