## 6 Results and Discussion  
### Evaluation on Asphalt Pavement Rutting Prediction Model  
Figure 6 shows the comparison between the predicted value of the model and the measured value during the long-term evolution of rutting of seven categories of structures. To evaluate the accuracy and prediction effect of the rutting prediction model quantitatively, the mean square error (MSE), root mean square error (RMSE), mean absolute error (MAE), mean relative error (MAPE), coefficient of determination (\(R^{2}\)), and other indicators between the predicted value of the rutting model and the measured value are calculated and summarized in Table 2. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline
**AC Type** & **AC10** & **AC13-I** & **AC13-II** & **SMA13** & **AC20** & **AC20** & **AC20** & **AC25** & **AC25** & **AC25** \\ \hline Asphalt Type & SBS & SBS & SBS & SBS & AH30 & AH50 & SBS & AH30 & AH50 & AH70 \\ \hline Permanent Deformation (mm) & 2.40 & 1.54 & 1.65 & 1.82 & 1.70 & 2.67 & 1.30 & 1.96 & 2.12 & 2.82 \\ \hline \end{tabular}
\end{table} 
Table 1: Permanent deformation of asphalt mixture rutting test. Figure 6: _Cont._ \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{2}{c}{**Structure Type**} & **MSE** & **RMSE** & **MAE** & **MAPE** & \(\mathbf{R}^{2}\) \\ \hline \multicolumn{2}{c}{**Unit**} & \multicolumn{2}{c}{**mm\({}^{2}\)**} & **mm** & **mm** & **-** & **-** \\ \hline \multirow{3}{*}{I} & STR1 & 1.16 & 1.08 & 0.91 & 18.3\% & 0.6346 \\  & STR2 & 1.12 & 1.06 & 0.85 & 17.6\% & 0.6223 \\  & STR4 & 7.70 & 2.78 & 2.40 & 53.7\% & \(-8.2491\) \\  & STR5 & 3.67 & 1.92 & 1.69 & 32.1\% & \(-1.2133\) \\  & STR7 & 3.52 & 1.88 & 1.64 & 25.2\% & 0.3337 \\  & STR8 & 5.68 & 2.38 & 2.29 & 30.9\% & 0.2222 \\  & STR10 & 5.63 & 2.37 & 2.20 & 30.5\% & 0.0469 \\  & STR12 & 3.09 & 1.76 & 1.35 & 23.0\% & 0.0860 \\  & STR11 & 2.89 & 1.70 & 1.43 & 23.1\% & 0.4220 \\  & STR13 & 2.45 & 1.56 & 1.26 & 21.8\% & 0.2500 \\  & STR16 & 2.67 & 1.63 & 1.31 & 24.4\% & 0.0444 \\  & STR17 & 1.72 & 1.31 & 1.15 & 23.1\% & 0.2084 \\  & STR18 & 7.23 & 2.69 & 2.20 & 25.3\% & \(-0.0792\) \\  & STR19 & 5.51 & 2.35 & 2.01 & 31.8\% & \(-1.0787\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Error between the predicted value of the rutting model and the measured value. Figure 6: Comparison between the predicted value of the model and the measured value. **(a)** Structure I-STR1. **(b)** Structure I-STR2. **(c)** Structure II-STR4. **(d)** Structure II-STR5. **(e)** Structure III-STR7. **(f)** Structure III-STR8. **(g)** Structure IV-STR10. **(h)** Structure IV-STR12. **(i)** Structure V-STR11. **(j)** Structure V-STR13. **(k)** Structure VI-STR16. **(l)** Structure VI-STR17. **(m)** Structure VII-STR18. **(n)** Structure VII-STR19. It can be seen from Figure 6 and Table 2 that: (1) For Structure I, the predicted value of the rutting model is relatively close to the measured value. The measured result fluctuates up and down near the prediction curve, and the error of the model prediction is small. For STR2 with the smallest error, the MSE is 1.12 mm\({}^{2}\); the RMSE is 1.06 mm; the MAE is 0.85 mm; and the MAPE is 17.6%. The \(R^{2}\) of STR1 and STR2 rutting models are 0.6346 and 0.6223, respectively. According to [12], the \(R^{2}\) of the predicted value of the model and the measured value in MEPDG is 0.6425. For Structure I, the accuracy of the rutting model in China's Specifications is basically equivalent to that in American MEPDG, and the model has a similar prediction effect. (2) For Structures II and VII, the correlation between the predicted value of the rutting model and the measured value is similar. A great difference is observed between the predicted value and the measured value of the rutting model with the two categories of structures. The predicted value is significantly larger than the measured value. The predicted curve is above the measured value. In addition, with the increase in the cumulative number of ESALs, the error in the model prediction rises.