# Smart Intersections and Connected Autonomous Vehicles for Sustainable Smart Cities: A Brief Review
## 1 Introduction  
Unprecedented urbanization and advancements in transportation technologies necessitate safer, faster, and more sustainable mobility solutions. Despite recent efforts to reduce road accidents, they are still a principal problem for enhancing road transportation systems. There are estimated to be around 1.19 million road traffic deaths worldwide yearly, incurring significant financial and non-financial costs to societies and governments. For instance, traffic death costs range from one to three per cent of the Gross Domestic Product (GDP) [1]. Even in developed countries, the number of fatalities and injuries resulting from these accidents remains significant. Italy, as an advanced and industrialized country, reported 3039 deaths and 224,634 injuries due to traffic crashes in 2023 [2]. As a result, improving the safety of road networks is one of the main objectives of decision-makers. Among the diverse components of road infrastructures, intersections perform a pivotal role in urban traffic management by facilitating the safe and efficient movement of vehicles, pedestrians, and cyclists. This is despite the high rate of accidents that occur at intersections, especially in urban areas. According to the AAA Foundation for Traffic Safety report, between 2010 and 2019, about 39 per cent of urban road traffic deaths in the United States were related to intersections [3]. Meanwhile, with the rapid progression of technological advancements and the emergence of novel innovations, a promising opportunity has been created to design smarter intersections to improve safety and enhance performance. By leveraging the technologies required for smartness, smart roads can create a transformative change in increasing sustainability, safety, innovation, and inclusiveness. Thesesmart infrastructures will be developed to redefine interactions among vehicles, users, and road environments by integrating advanced technologies, particularly autonomous vehicles (AVs) and connected and automated vehicles (CAVs). They will leverage cooperative intelligent transportation systems (C-ITSs) to facilitate seamless vehicle-to-vehicle and vehicle-to-infrastructure interactions. In addition to using various sensors capable of detecting performance, safety, and environmental factors, these roads will also utilize complementary technologies such as dedicated AV/CAV lanes, IoT-based surveillance systems, dynamic traffic management measures, and infrastructure capable of harvesting energy. Transportation Management, Data Analytics, and Vehicle-to-Everything (V2X) communication in real-time traffic management in smart intersections, cornerstones of intelligent transportation systems (ITSs), converge in core ITS components that lead the way towards sustainable urban mobility. These intersections combine digital technology sensors and real-time traffic monitoring systems [4; 5; 6], stepping beyond conventional intersections (e.g., signalized intersections). Intelligent junctions have gained attention in the scientific community (see Figure 1). The rapid development of connected vehicle technologies and emerging AI-driven traffic management for urban sustainability policies place advanced intersections as hotspots of next-generation urban mobility systems [7; 8]. Most of the literature on smart intersections has highlighted isolated technological practices (e.g., adaptive signal control and connected autonomous vehicle (CAV) coordination challenges). This review addresses the following key research questions:  
* What are the most effective approaches to evaluating the performance of smart intersections? * What are the challenges and opportunities for integrating smart intersections into smart city ecosystems? * How should future research directions be prioritized to maximize smart intersection technologies toward sustainable, inclusive, and resilient urban mobility systems?