# Automated Trucks' Impact on pavement Fatigue Damage
## 4 Discussion
In addition, these findings recommend using segregated lane distribution together with the uniform-wander mode only if wider lanes (e.g., 3.5 m) are present in the era of AT deployment, in order to further reduce pavement fatigue damage in the long term (see Table 2). * The aggravator scenarios are observed using a narrower lane of 3 m in both zero- and uniform-wander cases and in the lane width of 3.5 m only when the zero-wander mode is implemented. This is in line with the findings of [PERSON] et al. [16], indicating that autonomous trucks' lateral distribution increases fatigue damage at the bottom of the asphalt layer compared to traditional trucks, emphasising the need for proper lateral control to mitigate this impact. Comparing the DI values of different market penetrations revealed that the increased DI values of AT scenarios are more pronounced in the higher market penetrations than the lower ones and in the zero-wander scenarios than the uniform-wander ones. [PERSON] et al. [16] also argued that the damage increases with a higher proportion of ATs. * Although using the uniform-wander mode could result in lower fatigue damage than the zero-wander mode, this could still cause more damage than the non-AT scenarios for the narrower lane of 3 m. Thus, in the DI aggravator scenarios, the increased fatigue damage percentages induced by ATs are considerable, and further actions, such as increasing the thickness or stiffness of the layers, should be performed to mitigate their negative impact on pavement fatigue performance. * A practical implication for lane distribution management is recommending integrated lane distributions for ATs (i.e., compared with segregated cases) in the DI aggregator scenarios. This could reduce the adverse negative impact of AT deployment on pavement fatigue. * Comparing the effect of increased surface layer thickness and base layer thickness on the reduced percentages of DI values (see Table 2) revealed a practical implication that the use of a thicker surface layer could be more effective in mitigating the ATs' negative impact on pavement fatigue damage than the use of a thicker base layer for the zero-wander mode (see Figure 11a). In contrast, when using the uniform-wander mode, the observed results are the other way around, meaning that the thicker base layer could be more effective in reducing fatigue damage (see Figure 11b). However, an economic analysis study is needed to compare the costs of increasing the surface and base layer thickness and the benefits of prolonging the pavement life and reduced maintenance costs obtained from each DI mitigation solution. * Increasing the stiffness of the surface and base layer could result in reduced maximum DI values for the zero-wander mode, with more pronounced differences in the higher penetration rates. These results indicate that the stiffness of the base and surface layer plays a crucial role in mitigating the impact of ATs' wander mode on the pavement's fatigue performance. Notably, the reduced rates of maximum DI values caused by an increased surface layer stiffness are significantly lower for the uniform-wander mode compared to the zero-wander mode. Furthermore, in agreement with the findings of [PERSON] et al. [8], the present study showed that the increased thickness of the HMAlayer has a more significant impact on reducing fatigue damage than its stiffness for the zero-wander mode cases (see Figure 11a). * The reduced percentage rates of maximum BUDI values caused by increased base layer stiffness are around 75.51% to 76.88% in all the penetration rates, which indicates that the effect of base layer stiffness on fatigue performance is consistent across different levels of market penetration rates, and is consistently higher compared to the impact of surface layer thickness increase (see Figure 11).