With the rapid development of the low-altitude economy, particularly represented by urban air mobility, low-altitude airspace is expected to present characteristics such as high frequency, high density, heterogeneity, and dynamic operations. Traditional operation safety assessment systems, which are predominantly rule-driven and offline verification-based, are no longer sustainable in terms of reliability and real-time performance. There is an urgent need to reshape the entire system through a new methodology centered on digital twin technologies. To this end, this paper systematically elaborates on a cloud-edge-terminal collaborative architecture of the digital twin of low-altitude transportation systems. Within this architecture, the cloud layer serves as the twin hub, constructing a global digital environment; the edge layer covers key nodes, completing the aggregation and fusion of multi-source sensing data; and the device layer, primarily composed of aircraft, acts as the sensed objects while also undertaking responsibilities such as data reporting and command execution. Focusing on this architecture, this paper sorts out collaborative and non-collaborative perception methods within advanced low-altitude sensing systems, which form the data foundation supporting digital twin modeling, mapping, and scenario driving. For high-fidelity mapping of complex elements in low-altitude transportation, two core objects, the digital twin environment and the digital twin aircraft, were defined, and twin simulation platforms and tools for system testing and algorithm validation were summarized. It also sorts out the standardized operations safety assessment system based on digital twin and reviews quantitative operations safety assessment technologies, providing a scientific basis for the design, certification, and policy-making of low-altitude transportation systems.

The low-altitude economy is expanding urban mobility and service systems from ground-based networks to three-dimensional urban space. However, its large-scale deployment depends not only on aircraft technologies, but also on reliable operational infrastructure for communication, navigation, surveillance, meteorological sensing, computing, and safety supervision. This paper argues that smart infrastructure originally developed for connected and automated vehicles can provide a reusable foundation for low-altitude operations. Because low-altitude public routes are likely to follow existing urban corridors such as roads, railways, rivers, and utility corridors, there is strong spatial overlap with ground-based intelligent transportation infrastructure. By extending these capabilities upward, cities can reduce duplicate investment, improve infrastructure utilization, and support safe, scalable, and city-level air-ground operation management. 

Vehicle platooning offers significant advantages, including improved fuel economy, reduced congestion and collisions, and decreased air resistance, owing to synchronized acceleration and braking within the platoon. In a vehicle platoon, vehicle-to-vehicle (V2V) communication plays a pivotal role in facilitating information transmission between leading vehicle (L+V) and following vehicle (FV). However, existing V2V communication solutions, such as Dedicated Short-Range Communications (DSRC), Cellular Vehicle-to-Everything (C–V2X), and Visible Light Communication (VLC), face limitations, including high costs, infrastructural and network demands, and privacy concerns. To overcome these challenges, our research introduces a novel vision-based, network-independent information transmission approach. This method can be used as a complement to traditional V2V methods, especially under poor network conditions or potential attacks from adversaries. Simulations and experiments reveal that our approach can facilitate vehicle-to-vehicle information transmission even when network conditions are completely absent, thereby enhancing driving safety. This is achieved through the use of an LED matrix embedded in the leading vehicle′s taillight for communication. This innovative approach holds promise as a solution to the challenges associated with conventional V2V communication methods.