# Automated Trucks' Impact on pavement Fatigue Damage
## 1 Introduction  
Pavement structure analysis and design are crucial in ensuring that pavement can effectively accommodate truck traffic. In recent years, the implementation of automated driving technology into trucks has garnered significant attention due to its potential to provide a range of benefits to freight transportation, including reduced operational costs, improved fuel efficiency, and enhanced road safety [1; 2; 3; 4; 5; 6; 7]. However, it is essential to consider the potential differences between automated trucks (ATs) and human-driven trucks (HDTs), which could impact pavement performance differently [1; 2; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21]. Among the potential differences between ATs and HDTs, one of the critical factors to consider is the programmable capability of ATs' lateral wandering pattern. This capability allows ATs to follow a pre-programmed wander mode either individually within a lane or in a synchronised manner (i.e., truck platooning). In other words, we can envision two primary approaches for implementing the proposed wander modes for ATs: individual wandering and cooperative wandering. In the individual wandering approach, each AT swings within its lane, adhering to the proposed wander mode. This means that the lateral position of each vehicle would vary over time, similar to the behaviour observed in HDTs. Each vehicle's lateral movement would be independent, creating a dynamic pattern within the lane. In contrast, the cooperative wandering approach involves synchronising the lateral positions of all ATs within a platoon. Here, the lateral position of each vehicle would be fixed but slightly offset from one another. This synchronisation means that the number of ATs at each transverse point would collectively form the proposed wandermode. However, achieving the cooperative wandering approach realistically hinges on the presence of connected vehicle technology, a sufficient number of ATs, and supporting infrastructure. This interconnectivity allows for precise synchronisation and coordination among the vehicles, ensuring their lateral positions can be adjusted in real-time to maintain the desired wander pattern. Without such technology, the coordination required for the cooperative wandering approach would be exceedingly challenging. Researchers have proposed various potential wander modes, including zero, uniform-time, uniform-frequency, two-section-uniform, normal, double peak Gaussian, and Laplace for ATs [8; 15; 16; 22; 23; 24]. These studies have indicated significant differences in the induced fatigue and rutting damage between different ATs' wander modes. However, it is essential to acknowledge that the impact of the wander mode of ATs on pavement performance is also influenced by additional factors such as lane distribution management, market penetration, lane width, and structural characteristics of flexible pavements, as discussed in the subsequent sections [9; 15; 16; 18; 21; 25]. As ATs gradually become more prevalent on roads, mixed traffic conditions involving different market penetration rates may arise. Alternatively, an exclusive lane may be designated for ATs. Combining the programmed wander mode of ATs with the normal lateral wandering of HDTs (i.e., integrated scenarios) or employing 100% ATs in a separated lane (i.e., segregated scenarios) can lead to various transverse wheel load distribution scenarios, which can affect pavement rutting and fatigue life. In this context, previous studies have demonstrated that as the market penetration rate of ATs increases, the impact of the wander mode of ATs on pavement fatigue performance becomes more pronounced [16]. Due to the ATs' controlled wandering system, researchers have indicated that ATs have the potential to use narrower lanes, which could save construction and maintenance costs [26; 27; 28; 29]. However, using narrower lanes could considerably influence pavement performance in various wander modes and penetration rates, as [PERSON] et al. [9] demonstrated.