## 4 Results and Discussion
### Driving Stability Analysis on Multi-Factor
#### 4.2.4 Evaluation of Lateral Stability Based on CRG  
The entropy weight of each indicator was obtained in Table 6. It was found that the entropy weight of LA was 0.1806, and it has the lowest weight among the four indicators, which means LA has the poorest efficiency to characterize driving safety. The entropy weight of RA is 0.3112, so it indicates the greatest significance to driving safety. Then, it is followed by SA and LTR, and their entropy weights are 0.2904 and 0.2179, respectively. So, it is deduced that roll-over instability is more likely to occur due to the variation of seven factors, relative to sideslip instability. However, [PERSON] et al. (2019) identified that passenger cars tended to experience sideslips, which is not identical to this study. The distinction may be attributed to the extended consideration of pavement rutting in the present study.  
Figure 13: Coefficient matrix of Pearson’s Correlation.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Indications of Lateral** &
\begin{tabular}{c} **Driving** \\ **Speed** \\ \end{tabular} & **Rutting** & **Road Alignment** & & & **Adverse Weather** \\ \cline{2-8}
**Stability** & \(\mathbf{V_{\epsilon}}\) & **WHR** & \(\mathbf{R}\) & \(\mathbf{e}\) & \(\mathbf{\delta_{\text{lsw}}}\) & \(\mathbf{V_{\text{lsw}}}\) & \(\mathbf{f}\) \\ \hline LA & 0.7696 & 0.6189 & 0.6940 & 0.5950 & 0.5911 & 0.5762 & 0.6263 \\ SA & 0.7417 & 0.6444 & 0.6963 & 0.6467 & 0.5758 & 0.5913 & 0.6072 \\ LTR & 0.7052 & 0.6618 & 0.6793 & 0.6499 & 0.7131 & 0.6568 & 0.5998 \\ RA & 0.6374 & 0.8171 & 0.6020 & 0.5984 & 0.6064 & 0.5880 & 0.6111 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Grey relational grade (GRG) of each factor.  
Based on the GRG and entropy weight that have been obtained, a comprehensive relation grade (CRG) was calculated from Equation (15), and the results are shown in Figure 14. It indicates that vehicle speed and WHR of rutting have the leading effects on driving stability, followed by the radius of circular curve, superelevation, crosswind angle, crosswind speed, and friction coefficient, respectively. The CRGs of driving speed and WHR are both close to 0.7, which shows high significance in affecting the lateral stability of the vehicle. The radius of the circular curve and superelevation are also important factors that influence the lateral stability of the vehicle, which confirms the findings of [PERSON] et al. [64]. The differences in CRGs between crosswind angle, crosswind speed, and friction coefficient are rather small, three factors which have nearly identical effects on the lateral stability of the vehicle.  
Seven factors obviously influence driving safety. Firstly, the driving speed of the vehicle is generally the first, and most significant, factor when crossing rutting in adverse weather. Secondly, pavement rutting is the secondary factor that influences driving safety. In particular, the roll-over of the vehicle may take place while crossing the rutting immediately under poor road surface conditions with serious rutting distresses. Thirdly, road alignment is still the key consideration for driving safety, including the radius of the circular curve and superelevation in this study. If such an occasion happens with a fierce wind, the degree of risks may increase correspondingly. Moreover, the change in the road friction coefficient, due to the influence of adverse weather increases the possibility of occurring driving accidents. These unfavorable factors should be taken into account.