# Smart Intersections and Connected Autonomous Vehicles for Sustainable Smart Cities: A Brief Review
## 7 Integration of Smart Roads and Smart Intersections into Smart City Ecosystems  
The widespread implementation of advanced intersections in smart cities may have huge mobility benefits for several reasons. They allow for the efficient traffic flow of vehicles, pedestrians, and cyclists and work to improve traffic network operation in cities. Additionally, they coordinate with Adaptive Traffic Signal Systems (ATSSs) to change signal timing in real time to respond to traffic load fluctuations, pedestrian demand, and the need for emergency vehicles [77; 167]. Advanced intersections also support various transportation modes, including cars, public transit, and micro-mobility solutions (e-scooters and bikes) coordinated with pedestrian crossings, creating sustainable urban mobility [168; 169; 170]. Furthermore, they play an important role in the prevention of bottlenecks and reduction in congestion [171; 172]. In addition, next-generation roads are critical for improving public transit systems and Mobility-as-a-Service (MaaS) integration in urban spaces. They can plan to detect the approach of buses, trans, and High-Occupancy Vehicles (HOVs) and modulate vehicular traffic signals to reduce delays and increase transit reliability [173; 174]. They also exchange real-time data with MaaS systems to optimize the routing of ride sharing [175; 176]. By generating lower transportation expenses and fuel consumption, optimized traffic rules decrease commute times for everybody, from commuters to businesses [177]. Next-generationroads provide equal opportunities for transportation resources, sensitive pedestrian safety, and crossings for individuals in wheelchairs, as well as a fair transit service [178; 179; 180]. They contribute to increasing the quality of urban life by resulting in less traffic-related pollution, safer roads, and environmentally cleaner and safer cities [181; 182; 183]. Furthermore, they use data exchange systems based on 5G and 6G networks to reduce the response time for decisions and interactions between road infrastructures and autonomous vehicles [6; 184; 185; 186], apply all benefits offered by digital twin models [187; 188], and utilize vertically scalable hardware and software architecture, offering sustainable deployment across different urban environments with minimal disruptions [189; 190]. Despite their potential, several challenges have to be overcome. Among these is cross-platform interoperability, as smart intersections must share data with existing transportation infrastructure, traffic control centers, and city-wide mobility platforms easily for efficient system operation [191; 192]. Cybersecurity and privacy also pose significant concerns. Because they are all interconnected, smart intersections have to fend off cyberattacks and data breaches as well as prevent unauthorized access by developing secure encryption schemes, authentication protocols, and intrusion detection systems [193; 194; 195; 196]. Lastly, effective stakeholder collaboration is essential. For successful urban integration, collaboration between government agencies, technology providers, private companies, and local communities is needed to ensure intelligent intersections align with urban planning needs and public interest [197; 198]. Table 2 summarizes the key technologies, benefits, and challenges of smart roads in Smart Urban Mobility Systems. Implementing smart intersections requires a multidisciplinary approach and will not be limited to technological capabilities. Smart intersections with specific spatial and functional characteristics require appropriate urban planning to align themselves with the main direction of urban planning. For example, compact urban designs with multi-modal integration zones are more amenable to real-time coordination systems and pedestrian prioritization. At the same time, car-centric suburban environments may face obstacles to efficient deployment due to scattered traffic flows [199; 200].