# Road Infrastructure Challenges Faced by Automated Driving: A Review
## 1 Introduction  
Ensuring the health, livelihood and safety of people is a main concern in modern times. The World Health Organization reports that more than 1.3 million deaths are caused by road accidents [1]. Climate change is another concern that affects people's health and life quality. In 2018, transport was responsible for 24% of global CO\({}_{2}\) emissions, of which most were from road passenger (45.1%) and road freight (29.4%) transport [2]. These concerns are being addressed, as reflected by megatrends in mobility such as electrification, shared mobility, connected mobility and automated driving. In this study, we focus on automated driving and, in particular, its link to road infrastructure. The primary goal of automated driving systems (ADS) is enhancing road safety. [PERSON] et al. [3] showed, in 2011, that lane keeping assistance (LKA) would prevent 17% of fatal traffic accidents in Austria, and further enhance it by an additional 13%. [PERSON] et al. [4] investigated the influence of the forward collision warning (FCW) and lane departure warning (LDW) technology on traffic accidents. The authors concluded that FCW could prevent up to 69% of moderateto fatal driver injuries in rear-end collisions, and up to 22% of serious to fatal injuries caused by drift-out-of-lane crashes by using LDW. [PERSON] et al. [5] provided research estimating the benefits of combining multiple advanced driver assistance systems (ADAS) on accident prevention. The research estimated that approximately 40% of all passenger-vehicle crashes, 37% of crashes involved injuries and 29% of deaths in crashes could be prevented. More recent ADAS technology such as intelligent speed assistance (ISA) has the potential to reduce accidents by 30% and deaths by 20%, see [6]. However, misuse of advanced technology potentially leads to distracted driving, which is already showing an increasing trend as an accident factor. Moreover, partial automation causes earlier signs of sleepiness than manual driving [7]. Therefore, developing highly reliable ADAS is essential. To achieve a high level of reliability, ADAS must be improved through onboard perception sensors, decision logic and controllers. However, this may not be enough. A certain improvement in the road infrastructure also plays a role in achieving the desired level of reliability and, yet, road infrastructure design has been guided by human drivers. Ambiguous traffic signs and road markings can lead to recognition failure by ADAS, regardless of its causes, design patterns, insufficiently maintained road infrastructure and nonharmonised appearances of traffic signs and road markings. Sensor fusion and digitalisation of the road network through vehicular communication and digital maps offer promising solutions to increase the reliability of the entire system by providing redundancy. Moreover, such an approach promotes the implementation of a safety culture as a vital part of establishing functional safety within an organisation and the life cycle of a product, as recommended by ISO 26262 [8]. The synergy between ADS and road infrastructure is a well-recognised topic for inquiry that has been increasingly addressed in recent years. One of the first comprehensive studies on this topic was conducted in the US as part of the National Cooperative Highway Research Program project [9]. The investigation was based on a field study examining the effect of the quality of longitudinal white and yellow road markings on the detectability and readability of machine vision (MV) systems in vehicles. Similar extensive studies were conducted by Austroads, which examined the performance of lane keeping assist (LKA) and traffic sign recognition (TSR) based on literature research, stakeholder consultation and on-road and off-road tests [10; 11]. They aimed to specify recommendations for changes in Australian and New Zealand road infrastructure as well as to specify the level of required maintenance to support MV systems.