Automated Vehicles' Impact on Rutting and Fatigue Distresses in Flexible Pavements

Abstract

Automated vehicles (AVs) represent a significant leap forward in transportation engineering, promising to transform our relationship with mobility. As AVs become a reality, it is essential to understand their impact on road infrastructure. This transition demands examinations of how AVs will interact with road pavements, potentially altering patterns of distresses. In other words, AVs offer numerous benefits, such as optimised driving patterns, reduced energy consumption, lower pollution levels, improved traffic flow, and enhanced safety by minimizing human errors. Despite these advantages, it is crucial to consider their impact on pavement infrastructure, as AVs potentially differ from humandriven vehicles (HDVs). Differences in lateral movement patterns, lane width requirements, penetration rates, and lane distribution can all affect pavement performance and longevity. Understanding these differences is essential for adapting road designs and maintenance strategies to ensure infrastructure sustainability. Addressing these factors will help maximise the benefits of AVs while maintaining durable road systems. Despite the significant technological advances and potential benefits of AVs, there is a notable gap in understanding how AVs and HDVs differently impact pavement performance. Current research lacks comprehensive studies comparing the long-term effects of these vehicles on pavement performance, particularly regarding pre-programmed wandering patterns, mixed traffic conditions, lane width, and pavement structural characteristics. Addressing these research gaps is essential for designing appropriate pavements that can support both AVs and HDVs effectively, ensuring the long-term viability of road infrastructure. This dissertation titled "Automated Vehicles Impact on Rutting and Fatigue Distresses in Flexible Pavements" aims to investigate the impact of AVs on pavement rutting and fatigue performance, focusing on flexible pavement structures. The research addresses five primary objectives: assessing the comparative impact of AVs relative to HDVs, exploring how different lateral movement patterns (i.e., wander modes) of AVs affect pavement performance, examining the influence of lane widths tailored for AV traffic, assessing the impact of varying market penetration rates of AVs on pavement loading patterns, and evaluating the effects of flexible pavement layer thicknesses and material properties under AV-induced stresses. The methodology involved developing finite element models (FEMs) using ABAQUS software calibrated and validated by the experimental data of the Indiana Department of Transportation/Purdue University accelerated pavement tester (APT) facility. Various wander distributions for AVs (e.g., zero-wander and uniform-wander) and normal-wander for HDVs were simulated across different lane widths. The study assumed a 20-year design period with 30 million standard equivalent single axle loads of 80-kN to predict in-service pavement rutting and fatigue. Evaluation scenarios considered various combinations of lane width, wander mode, and market penetration rates to assess their combined effects on pavement performance. Multiple pavement layers with varying thicknesses and material properties were integrated to evaluate their impact on rutting and fatigue. Key findings indicate that AVs, with their precise, controlled movement patterns, have a distinct impact on pavement rutting and fatigue compared to HDVs. The zero-wander mode results in significant rutting at specific transverse positions, while the uniform-wander mode distributes the load more evenly, potentially reducing rutting depth compared to the zero-wander mode. Narrower lanes dedicated to AVs increase total rutting depth, highlighting the need for optimised lane width designs to balance safety, pavement performance, and construction costs. Increasing AV penetration rates alters transverse loading patterns, influencing both rutting and fatigue performance. Mixed traffic conditions require adaptive strategies in pavement design. Pavement layersthickness and material properties significantly affect the pavement s ability to withstand AV-induced stresses, emphasising the need for improved material and adapted thickness configurations. This research advances both theoretical understanding and practical strategies for enhancing pavement performance amidst AV deployment. Some practical recommendations include the following: Initially, AVs will likely be introduced on roads under mixed traffic scenarios with low market penetration rates. In such settings, if AVs default to a zero-wander mode, this could exacerbate pavement rutting and fatigue. Therefore, implementing a uniformwander mode for AVs is recommended to mitigate early pavement deterioration. In scenarios with narrower lanes, enhancing pavement layer material, thickness, and stiffness becomes crucial if lane widening is not feasible. As we progress towards segregated lanes and higher AV penetration, potentially 100% AV traffic, the risk of accelerated pavement fatigue and rutting increases. Thus, continued use of a uniform-wander mode, along with wider lanes and improved pavement thickness and stiffness, is essential. These strategic infrastructure adjustments are vital to ensure that the transition to AV dominance does not compromise pavement longevity. This research provides practical recommendations for adapting pavement infrastructure to support the sustainable integration of AVs, ensuring road resilience against evolving traffic dynamics.