# Automated Trucks' Impact on pavement Fatigue Damage
## 4 Discussion  
The simulation results in this study present various quantitative comparisons between the fatigue damage incurred by distinct pavement structures that have undergone exposure to the normal-wander mode of HDTs mixed with the zero- and uniform-wander modes of ATs, considering different market penetrations and lane widths. These comparisons offer several insights that can provide practical considerations regarding the impact of AT deployment scenarios compared with the non-AT scenarios and identify the cases that could lead to accelerated fatigue damage in the long term. Furthermore, this research provides practical suggestions, such as improving layers' thickness and stiffness to mitigate the adverse effects of increased damage and alleviate potential challenges associated with AT deployment. In other words, comparing different pavement structures subjected to different load distribution scenarios revealed significant differences in the fatigue damage incurred by the pavements. This suggests that pavement designers and managers should consider the ATs' penetration rate and wander patterns when selecting appropriate lane widths or pavement materials and thicknesses in their designs. The subsequent sections discuss the present study's findings and their implications. * Comparing the DI values resulting from the introduction of ATs on roads to scenarios featuring only HDTs revealed that AT deployment could either decrease the fatigue DI (i.e., 'DI mitigator scenarios') or increase it (i.e., 'DI aggravator scenarios'), depending on the AT deployment scenarios. For instance, in the case of adopting a uniform  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Lane Width** & \multicolumn{3}{c}{**3 m**} & \multicolumn{3}{c}{**3.5 m**} \\ \hline
**Scenario** & **Integrated** & \multicolumn{3}{c}{**Segregated**} & \multicolumn{3}{c}{**Integrated**} & \multicolumn{3}{c}{**Segregated**} \\ \hline
**Market Penetration Rate** & **20\% to 80\%** & \multicolumn{3}{c}{**100\%**} & \multicolumn{3}{c}{**20\% to 80\%**} & \multicolumn{3}{c}{**100\%**} \\ \hline Wander Mode of ATs & Zero & Uniform & Zero & Uniform & Zero & Uniform & Zero & Uniform \\ \hline \multirow{3}{*}{Percentage Change of DI Compared to the Reference Scenario (0\% ATs)} & +37.67\% & +11.6\% & \multirow{3}{*}{+233.57\%} & \multirow{3}{*}{+58.01\%} & \multirow{3}{*}{to} & \multirow{3}{*}{+28.92\%} & \multirow{3}{*}{\(-1.41\%\)} \\  & to & to & & & & & & to & \\  & +184\% & +46.41\% & & & & +221\% & \(-5.64\%\) & \\ \hline \multirow{3}{*}{Aggravator/Mitigator} & Aggravator & Aggravator & Aggravator & Aggravator & Aggravator & Aggravator & Mitigator & Aggravator & Mitigator \\ \hline \multirow{3}{*}{Reduced Percentage of DI by Increasing the HMA Layer’s Thickness from 10 cm to 20 cm} & \multirow{3}{*}{\(-17.59\%\)} & \multirow{3}{*}{\(-0.60\%\)} & \multirow{3}{*}{\(-42.92\%\)} & \multirow{3}{*}{\(-1.76\%\)} & \multirow{3}{*}{NA\({}^{*}\)} & \multirow{3}{*}{\(-42.92\%\)} & \multirow{3}{*}{NA} \\  & to & & & & & & & \\  & to & & & & & & & \\  & to & & & & &  
wander mode for ATs on a 3.5 m wide lane, the deployment of ATs does not negatively impact pavement fatigue performance compared to the non-AT scenarios. In contrast, it may even slightly decrease the DI values. This reduction is more considerable in the segregated scenarios than in the integrated ones. This finding is in agreement with the findings of [PERSON] et al. [16], indicating that in the worst-case scenario where only zero-wander-distributed trucks are on the pavement, the fatigue damage is 2.7 times that of human-driven trucks. Conversely, for other lateral control modes, higher proportions of autonomous trucks result in less fatigue damage, extending pavement life. * The findings of this study support the previous findings of [PERSON] et al. [15] and [PERSON] et al. [17], recommending the use of uniform-wander mode for ATs compared to zero-wander mode.