URBAN DENSITY AND AUTONOMOUS VEHICLE: COMPARATIVE INSIGHTS FROM CHINA AND THE UNITED STATES A Dissertation Presented to the Faculty of the Graduate School of Cornell University in Partial Fulfillment of the Requirements for the Degree of Master of Science by Shi Yan December 2025 ©2025 Shi Yan ABSTRACT This paper examines the deployment of autonomous vehicles (AVs) across different urban densities, focusing on the cases of China and the United States. While much existing research focuses on technological breakthroughs or national policies, I am more interested in understanding how urban form influences the direction, pace, and outcomes of AV deployment. To explore this question, I develop a framework linking policy instruments, technological strategies, and urban density. I apply this framework to a series of city-level case studies, including Beijing, Suzhou, Chengdu, New York, Pittsburgh, Chicago, San Francisco, and Phoenix, as well as rural areas such as Shanxi and suburban Arizona. I also draw on the social construction of technology theory (SCOT) to understand the role of different social groups in the development and implementation of AV technology. The analysis reveals that population density, in addition to being a contextual factor, is a key variable. In densely populated cities like Beijing and New York, the complex road environments require strong coordination between the deployment of AVs and public infrastructure and regulations. In China, the dense population forces the government to prioritize dense infrastructure, such as vehicle-to-everything (V2X). In contrast, American cities like San Francisco and New York often rely on private industry to drive innovation, resulting in autonomous vehicles with more robust onboard intelligence. However, how to effectively integrate them into urban systems remains an unresolved issue. The differences are equally striking in less densely populated cities like Suzhou and Pittsburgh. The Suzhou government actively plans to integrate autonomous vehicles into its industrial parks, even developing China's first smart highway. In Pittsburgh, early industry-university- research collaborations helped initiate autonomous vehicle testing, but a lack of sustained public policy support has slowed its wider adoption. This suggests that moderately dense cities may have the potential to combine flexibility with infrastructure investment, provided governance capacity is aligned. In low-income and rural regions with relatively low population density, both China and the United States are gradually leaning toward a more car-centered strategy. Because the costs of building advanced infrastructure are high while the expected returns remain limited. For example, in Arizona, companies like Waymo have begun operating autonomous vehicle services in suburban communities. Meanwhile, in rural China, supported by simplified policies and relatively practical technology, companies are actively experimenting with autonomous vehicles in areas such as logistics and last-mile delivery. Overall, this paper demonstrates that while population density plays an important role, political institutions and governance models often override or reshape these spatial constraints. For example, China’s top-down governance structure enables many medium-sized cities to take a proactive role in planning and investing in AV-related infrastructure. In contrast, American cities tend to rely more on market-driven experiments led by private companies. As a result, even cities with similar population densities can have very different trajectories for autonomous vehicle development in both countries. iii BIOGRAPHICAL SKETCH Shi Yan is a master’s student in the Regional Science program in the Department of City and Regional Planning at Cornell University. His research examines the interaction between emerging technologies and urban development, with a particular focus on how autonomous vehicle deployment varies across different urban densities and governance systems in China and the United States. Before coming to Cornell, he completed his undergraduate studies at Pennsylvania State University and majored in Geography, where he developed an interest in geographic information system and spatial analysis. During his graduate study, he has also gained experience with GIS technologies, data analysis, and comparative policy research. iv ACKNOWLEDGEMENTS I am deeply grateful to my advisor, Professor Stephan Schmidt, for his generous guidance, patience, and encouragement throughout the dissertation writing process. His advice prompted me to focus more on the contrasting political systems of China and the United States, which provided me with unexpected insights. I am also deeply grateful to my dissertation committee member, Professor John Carruthers, for his thoughtful feedback and constructive suggestions that helped me refine my argument. I am also grateful to the Department of City and Regional Planning at Cornell University, and particularly the Regional Science Program, for providing an intellectually stimulating environment and the opportunity to learn from colleagues from diverse academic and cultural backgrounds. I am especially grateful to my classmates and friends in the program, whose discussions, encouragement, and friendship made my studies both fruitful and memorable. Finally, I would like to express my deepest gratitude to my family. Their unwavering support, love, and encouragement gave me the strength to pursue my graduate degree abroad and complete this dissertation. This journey would not have been possible without their unwavering belief. v TABLE OF CONTENTS Abstract Biographical Sketch .......................................................... iii Acknowledgements .......................................................... iv Chapter 1: Introduction .................................................. 1 Chapter 2: Literature Review ......................................... 2  2.1 Policy-Technology-Density Framework o 2.1.1 Policy Dimension o 2.1.2 Technological Dimension o 2.1.3 Density Dimension Chapter 3: Analytical Framework and Its Application .......... 8 Chapter 4: Comparative Case Study (United States vs. China) .... 14  4.1 Densely Populated Areas o 4.1.1 Policy Environment o 4.1.2 Technological Adaptability o 4.1.3 Urban Density and Development Impacts  4.2 Intermediate Density Areas o 4.2.1 Policy Environment o 4.2.2 Technological Adaptability o 4.2.3 Urban Density and Development Impacts  4.3 Low-Density and Rural Settings o 4.3.1 Policy and Technological Adaption vi o 4.3.2 Impacts of Low Urban Density on AV deployment Chapter 5: Summary Table ...................................... 36 Chapter 6: Discussion .................................................. 36 Chapter 7: Conclusion ................................................ 38 Chapter 8: Policy Recommendations ................................ 40 References .................................................................... 43 1 1. Introduction As early as 1925, only 40 years after Karl Benz invented the first truly modern car, an autonomous car designed by Francis Houdina came into existence. By receiving radio signals from the vehicle following, the vehicle accomplished the starting, steering, braking, and acceleration without the driver control (JALOPNIK, 2017). However, with the limitations of computer power and sensors, despite the efforts of scientists and engineers, no breakthroughs in autonomous driving technology have been achieved in the 55 years since then. At 80s, with the “NavLab” car invented by Carnegie Mellon University and "VaMoRs" launched by Mercede-Benz cooperated with Munich Federal Armed Forces University, they prove to the world the systematic application of computer vision and multi-sensor fusion technology in autonomous driving (Engineer.com, 2016). Entering the 21st century, autonomous driving technology has ushered in new development opportunities. Breakthroughs in computer computing power, the advent of LiDAR, and the application of AI end-to-end models have brought autonomous driving technology one step closer to realizing the vision of large-scale application and reshaping transportation methods. Based on the data collected by IDTechEx, as of 2024, leading companies such as Waymo, Cruise, and Baidu Apollo have deployed more than 2,000 L4 automation level taxis, with a cumulative test mileage of tens of millions of miles. Baidu operates 500 driverless taxis in Wuhan and plans to expand to 1,000 by the end of 2024. Moreover, one of the leading companies, Tesla, collected real road data through more than 1 million mass-produced vehicles, with a cumulative mileage of billions of miles by the end of 2024 (Tesla Inc, 2025). 2 This paper explores the qualitative differences in the formulation of autonomous driving policies and the direction of technological development at different urban densities. With the insight of cities in the United States and China, I compare their policy framework, technology adaptability, and development impacts at different urban densities. Three types of cities are evaluated systematically: a) Densely Populated Areas (Beijing & Shanghai vs. New York City & San Francisco); b) Intermediate Density Areas (Suzhou & Chengdu vs. Pittsburgh & Chicago); c) Low-density or Rural Areas (Yangquan vs. Phoenix suburbs). The analytical framework of this study adopts the "policy-technology-density" approach. Under the perspective of the social construction of technology (SCOT), the complex interactions between policy choices, technological capabilities, and density-related urban conditions are analyzed. Specifically, the framework considers three interacting dimensions: (1) Policy Toolbox: regulatory approaches, subsidies, and pilot initiatives; (2) Technology Adaptability: assessing the capabilities, infrastructure complexity, and cost feasibility of autonomous vehicles (AVs) in different urban environments; and (3) Density Response Thresholds : studying how population, land use patterns, and transportation infrastructure capacity affect the feasibility and effectiveness of autonomous vehicle deployment. 2. Literature Review: AV Integration Witnessing the booming development of the autonomous driving industry, what impact will it have on urban development? Supporters argue that the widespread use of self-driving cars can 3 improve road safety by reducing accidents caused by human error and reduce emissions through smoother driving and electric automation (nyc.gov, 2024). According to academic estimates, if self-driving cars are widely used in cities, they can reduce urban greenhouse gas emissions by about one-third (Makahleh, 2024). These potential advantages make the widespread use of self-driving cars a major concern in densely populated urban areas with heavy traffic, frequent accidents and pollution. Therefore, how to integrate autonomous vehicles (AVs) into urban transportation networks has been one of the most popular research directions in the field of urban transportation in recent decades. AVs can perceive the environment and navigate without human intervention, thus improving safety, reducing emissions and improving efficiency in urban spaces (Fagnant & Kockelman, 2015). Due to the fact that AV technology is an emerging industry, which presents some regulatory challenges to society, cities and countries are developing policy frameworks to guide this transition. AV integration requires appropriate policies to manage regulations for AV testing, traffic safety requirements, infrastructure investment to support AV technology, and coordination with broader and long-term urban planning goals. As the major countries, both geographically and economically, China and the United States have made different attempts at AV’s integration. In the United States, the approach to AV policy is decentralized and often city-specific. As for now, there is no national law mandating how AV should be integrated while state and local government take the lead in regulation with the guidance provided by federal agencies. According to the State of AV 2024 published by Autonomous Vehicle Industry Association, as 4 of early 2025, 35 U.S. states have enacted laws regulating AV and several others have issued executive orders or are actively considering legislation. In China, national and local governments are actively promoting the deployment of AV as part of large-scale smart city initiatives. This is a top-down process: guided by the national-level strategy formulated by the central government, local pilot breakthroughs are made to drive the coordination of various supply chains and diversification of scenarios. For example, Beijing and Shanghai have implemented large-scale AV pilot projects, including vehicle-road cooperative (V2I) communication systems and dedicated AV test areas, leveraging the government's large investment in smart road infrastructure (Li et al., 2021). There is still a gap in systematically studying how different urban density environments affect AV integration, even though existing research has extensively explored autonomous vehicle (AV) technologies, deployment strategies, and their pervasive impacts on cities. This research gap highlights the need for a more comprehensive analytical framework that captures the subtle interactions between policies, technological capabilities, and urban density. The subsequent chapters will fill this gap by introducing a "policy-technology-density" analytical framework to compare cities in the United States and China. 2.1 Literature Review: Policy-Technology-Density Framework The Social Construction of Technology (SCOT) framework proposed by Pinch and Bijker in 5 the last century argues that instead of driven solely by technological logic, technological development is also shaped by social groups, values, and interactions (Lynch & Hu, 2022). In the context of autonomous vehicles (AVs), advances in AV technology in terms of design, regulation, and usage reflect the influence of stakeholders such as policymakers, industry engineers, consumers, and other social groups. Recent research on AVs emphasizes that the development of the AV industry should not only focus on the technical field, but also extend to the field of social values, and calls for examining AV development through the lens of SCOT rather than viewing its application as a purely technical or deterministic process (Waltermann & Henkel, 2024). Innovation in the AV industry is fundamentally inseparable from policy and regulatory orientation, public expectations, and cultural attitudes. To systematically analyze these interacting forces, this paper adopts a three-part coordinated framework, the 'Policy- Technology-Density' synergistic framework. 2.1.1 Policy Dimension Policy plays a key role in shaping the trajectory of AV integration. Everything from safety standards and testing protocols to subsidies and infrastructure investments are either constrained or driven by policy. California has become a pioneer in the AV industry, not only because of the dominant of its computer software and electronic components industries, but also because of its early policy support for AV. Extensive pilot projects by multiple companies in San Francisco's dense urban landscape have made it one of the most active AV testing sites in the United States (Stocker & Shaheen, 2017). Comprehensive AV trials have been conducted 6 early in California, providing a solution to the technical and social problems of high-density urban environments (Brodsky, 2016). In contrast, New York City has taken a more cautious regulatory stance, not allowing strictly regulated AV testing until 2020. Unlike San Francisco’s flat urban plan, New York City is known for its uniquely dense and complex urban environment, with high pedestrian traffic and a dense street grid. Beijing, in particular, has established an extensive test area covering hundreds of kilometers of urban roads in Yizhuang, equipped with sensors and advanced communication technologies (Liu & Wang, 2021). Shanghai has also promoted the popularization of AV by issuing licenses to companies such as Baidu and AutoX to operate autonomous ride-sharing services in clearly defined areas that provide a policy- driven integration approach (Li et al., 2021). Figure 1 High-level Autonomous Driving Demonstration Zone in Beijing Source: (UNECE) 2.1.2 Technological Dimension 7 Technology adaptability is another dimension that highlights the interaction between AV capabilities, infrastructure complexity, and economic feasibility. The success of AVs depends on their ability to cope with the complexity of urban environments, from high-density urban cores to sprawling suburbs (Fraedrich et al., 2019). AV technology development in the US focuses on vehicle self-sufficiency, using onboard sensors and artificial intelligence to navigate existing roads, rather than smart infrastructure. The “single-car” autonomous driving approach fits the US urban development model, where AVs are expected to be driven more on highways and suburban streets, so new infrastructure construction is minimal (Sever & Contissa, 2024). China’s AV technology roadmap prioritizes connectivity, reducing the reliance on vehicle- based technology by counting on smart city infrastructure. Urban pilots connect AVs with intelligent transportation systems and dedicated 5G communication networks. Researchers have focused on big data-connected AV which can relieve the burden of individual vehicles navigating chaotic urban environments and are networked with smart roads and traffic lights (Yue et al., 2024). This makes that China’s AV designs often include vehicle-to-everything (V2X) capabilities by default, and deployment priorities in complex urban areas tend to favor autonomous taxis and autonomous buses, as centrally managed fleets of AVs can ease congestion (Ding et al., 2022). 2.1.3 Density Dimension When people begin to consider how and where the AV should be deployed and integrated, 8 urban density is one of the factors that first comes to mind. Urban density significantly affects traffic patterns, infrastructure requirements and navigation complexity, making it an important variable for planning AV applications (Fraedrich et al., 2019). It is challenging even for human drivers to drive in high-density urban areas because the dynamic environment is so sophisticated - streets are packed with cars, buses, bicycles, and pedestrians that handling dense traffic and frequent interactions at intersections requires advanced capabilities and infrastructure support for AV. For example, a mature traffic light system, dedicated AV lanes, or ultra detailed digital maps are needed to ensure AV can process safely in a busy city center (Makahleh, 2024). In contrast, it is simpler for an AV to operate in low-density or highway environment since it focuses more on high-speed safety features rather than driving on streets with dense pedestrian traffic (Othman, 2022). Policymakers must tailor AV integration strategies to urban environments, as what works on quiet suburban roads may not work on crowded downtown avenues. Legislative frameworks need to be diverged to population density—large cities may introduce special rules that are not applicable to small towns, such as designating "zero-emission zones" or integrating AV services with public transportation (Kok, 2023). Thus, urban density should be a key consideration and a central theme when planning for AV deployment. 3. Analytical Framework and Its Application This section will elaborate on the “Policy-Technology-Density” analytical structure and explain how it will guide the subsequent comparative case studies between the United States 9 and China. The framework is established with three interrelated dimensions which are policy toolbox, technology adaptability, and density response threshold. Chart 1: Analytical Framework 3.1 Policy Toolbox Government policies offer a range of tools to influence the development and integration of AVs. Scholars have outlined a range of policy influences and interventions for autonomous mobility. They emphasize the need for proactive governance to maximize benefits and mitigate risks (McAslan, 2021). In practice, many jurisdictions have introduced specific rules for AV testing and operation, such as setting safety standards and licensing requirements, while some special jurisdictions maintain a relaxed environment to attract industry to experiment. In addition, fiscal incentives are another tool for governments. AV research, infrastructure investment, and early applications can be incentivized by strategic subsidies or tax credits. Well-designed AV Technology Policy Toolbox Rules that support or standardize the AV; Subsidies for infrastructure or technology development. Technological Adaptability Prerequisites for AV Technology; Cost- effectiveness of deployment strategies Urban Density Population density; land-use pattern; transportation network capacity 10 subsidies can accelerate the transition to the "dark ages" of early low market penetration by incentivizing continued innovation and us (Luo, 2018). Another key policy tool is to promote pilot projects and demonstration projects. Cities around the world have launched pilot projects for AVs (such as the Beijing Yizhuang test site mentioned earlier) to understand the feasibility of the technology in real-world applications. Pilot projects will allow private AV developers to test vehicles on public roads. This will then provide local authorities with insights into the impact of AVs on safety, traffic or fairness and allow them to formulate regulations or infrastructure plans accordingly. However, these experiments must be carefully coordinated with public goals, as they risk marginalizing broader planning discussions about the future of mobility if they are simply viewed as technical exercises (Cugurullo, 2021). 3.2 Technological Adaptability The second dimension focuses on how technical complexity and cost interact with urban characteristics. Autonomous driving systems must cope with the quality of infrastructure, street geometry, and unexpected traffic behavior in different urban areas. Early deployment is often limited to well-mapped areas with favorable conditions, because cities with orderly traffic and clearly marked roads can reduce sensor uncertainty, which is conducive to the initial operation of AVs. Therefore, the speed of the promotion of AVs depends to some extent on the ability of technology to handle the complexity of specific urban environments. Cost and infrastructure are also key factors in the adaptability of technology. Significant investments in vehicle technology, high-definition maps, vehicle-to-road communications, or dedicated lanes will lay 11 the foundation for large-scale deployment of AVs, such as designing a consistent lane marking system or new communication protocols (Bahrami, 2023). On the one hand, AV developers try to improve algorithms to adapt to local driving regulations and restrictions; on the other hand, governments and planners may need to install sensors or 5G coverage to support reliable AV operation. The high cost of autonomous driving technology is more easily accepted in terms of alleviating public transportation labor shortages or improving the safety of dangerous routes. Therefore, technical feasibility is closely related to urban conditions. Without supporting infrastructure and controllable complexity, even strong policy interventions may have little effect. 3.3 Density Response Threshold Density response threshold measures how urban density affects the impact and feasibility of AV deployment. The urban density is composed by several aspects of urban form which are population, land use, and transportation network capacity. 3.3.1 Population Density Population density is usually measured as the number of residents or jobs per unit area. High- density cities concentrate many potential passengers and destinations within a certain area, thus facilitating shared transportation modes and frequent public transportation services (Heinrichs, 2016). AV deployment is likely to focus on enhancing collective mobility. Because dense passenger flow ensures sufficient demand in a limited area, deploying fleets of autonomous 12 shuttles or robotaxis to supplement public transportation becomes a preferred option. In contrast, in low-density suburban or rural areas, residents rely more on private cars due to scattered development (Heinrichs, 2016). To fill the gaps in public transportation coverage, autonomous driving technology may mainly appear in the form of personal driverless cars or on-demand services rather than in the form of high-capacity shared fleets. Similar to traditional transportation, there may be threshold effects in the deployment of AVs. Below a certain density, it becomes challenging to operate a cost-effective shared autonomous driving service due to longer distances and fewer trip connections (European Environment Agency, 2025). Thus, this paper examines these thresholds, recognizing that population density can promote or limit the type of AV deployment that is practical in a particular area. 3.3.2 Land-Use In high-density cities, the concentration of housing, jobs, and amenities can reduce the need for long-distance car trips and make people more likely to choose alternative travel options such as walking, biking, and public transportation (Heinrichs, 2016). AVs can perfectly function as last-mile connections at transportation hubs or as autonomous shuttles in the city center. In contrast, in medium- and low-density cities, longer trips and a more car-dependent lifestyle driven by dispersed or segregated land use patterns can increase people's consideration of the advantages of AVs for long-distance travel. In fact, depending on how they are managed, AVs may further promote urban sprawl or promote urban density. Autonomous driving can make driving easier and make people more likely to live farther away from the city center, 13 thereby expanding the coverage of metropolitan areas. One study predicts that if AVs are popular in the United States, the urban sprawl area of the Dallas-Fort Worth Metropolitan Area will increase significantly by 68% (Moore et al., 2020). On the other hand, the spread of autonomous driving technology can also support higher-density development by reducing the need for parking spaces and improving land use efficiency in core areas. Existing parking spaces can be transformed and connected to AV facilities, making urban spaces more compact and efficient. Therefore, land use configuration and policy directions will determine whether the deployment of AVs will exacerbate urban sprawl or be consistent with a more sustainable, denser urban form. 3.3.3 Transportation Network Capacity The third density-related factor essentially refers to the ability of the road infrastructure to handle the volume of traffic. The introduction of AVs into urban traffic flows will have complex, nonlinear effects on traffic grid performance. Traffic engineering studies have shown that at low AV penetration, a small number of AVs mixed with a large number of human-driven cars will reduce effective capacity and increase congestion, because AVs tend to maintain larger safety gaps and drive more cautiously in front of unpredictable human drivers (Li, 2025). However, this situation will improve in the future as AV market penetration increases. Once the number of AVs reaches a critical level, estimated to be around 50% to 60% of traffic flow, efficiency benefits will accumulate through coordinated driving, reduced headway, and platooning (Liu, 2024). At that point, urban road capacity may be significantly improved, even 14 in high-density roads to relieve congestion. This threshold phenomenon means that the traffic benefits of AVs are highly dependent on density. Large, congested cities will see improvements only after AVs reach a certain level of penetration, while networks with less traffic in small cities can achieve smoother traffic even with a small number of AVs. In addition, the process of repositioning empty vehicles that have just completed service may lead to increased vehicle travel. Unrestricted AV use may lead to additional vehicle miles travel and weaken public transportation ridership (McAslan et al., 2021). To ensure that AVs enhance rather than block urban mobility at different densities, both infrastructure capacity upgrades and demand management policies, such as smart traffic lights or dedicated AV lanes (as mentioned before), will be needed. The following chapter will apply this three-dimensional framework to case studies of Chinese and American cities of varying densities, taking a close insight of how policy, technology, and spatial factors interact. 4. Comparative Case Study (United States vs. China) 4.1 Densely Populated Areas For the densely populated areas, I select Beijing, Shanghai from China and San Francisco, New York from United State as the case study. Based on the recent demographic data, all four cities possess large contiguous contiguous 1ௗkm² grid‑cells each contain ≥ௗ1ௗ500 inhabitants perௗkm², 15 and the contiguous cluster’s total population is ≥ௗ50ௗ000. City (core district) Average Population Density (per km²) Total Population (2025) Source Beijing 5,299 22.6 million World Population Review Shanghai 2,059 30.5 million World Population Review New York City 11314 8.8 million U.S. Census Bureau San Francisco 7,299 0.83 million U.S. Census Bureau Table 5.1: Population Density of Selected Cities in Densely Populated Areas 4.1.1 Policy Environment Chinese Mega-cities benefit an aggressive top-down policy pushing the AV industry. China's central government has issued nationwide guidelines and pilot projects to regulate the orderly deployment of AV. In Beijing and Shanghai, local governments have strongly supported the testing and services of AV by setting up dedicated areas, issuing licenses, and investing in infrastructure. By early 2024, Beijing had opened more than 1,160 kilometers of public roads for AV trials, and 18 companies had approved 384 AV for trials (The People’s Government of Beijing Municipality, 2024). Shanghai has similarly designated four testing areas and approved the deployment of 794 AVs on more than 2,000 kilometers of roads for pilots (Xinhua News, 2024). Both cities now allow limited commercial autonomous taxi services. For example, Beijing decided in mid-2023 to allow fully autonomous taxis (previously, each 16 autonomous taxi would be equipped with a human safety driver for safety reasons) to operate and charge in specific areas (Luo, 2023). This policy has benefited from a series of successful supervision pilots since 2019, as regulators have sufficient confidence in the success of the pilots. Shanghai plans to introduce Robotaxi in the busy Pudong district and has currently authorized several companies to provide such services, such as Baidu, AutoX, and Pony.ai. Overall, China's densely populated cities practice multi-level coordinated governance. First, the national ministries will formulate strategic goals (to achieve large-scale production of AVs by 2025), and then the municipal government will introduce local regulations that suit local conditions and promote the establishment of AV innovation pilot zones. There are no federal regulations for the deployment of AVs in the United States, so states and cities need to make their own. More than 60% of the U.S. autonomous taxi deployments are in California, which has become the center of the U.S. AV industry. San Francisco's policy is relatively open. The California Department of Motor Vehicles (DMV) and the Public Utilities Commission have developed a licensing process for AV testing and commercial operations. In 2024, Waymo and Cruise received licenses to operate 24-hour paid autonomous taxi services. San Francisco also became the first city in the United States to allow fully driverless fleets to operate commercially. Mayor Lurie has also publicly stated that AVs will be an important part of San Francisco's downtown revitalization plan (San Francisco Office of Mayor, 2025). He claimed that AV access will improve visitor flow to shops, theatersz and restaurants and complement Muni, taxis and bikes. In New York City, state law has set up strict barriers. In the early years, AV testing required police escorts. The mayor and the Department of 17 Transportation introduced a licensing system that requires all autonomous test vehicles to be equipped with safety drivers, who must receive professional training and be ready to take over at any time (New York City Office of Mayor, 2024). In addition, companies applying for testing need to submit historical test records including collision data and disengagement rates and prove that their technology can cope with the high density of pedestrians and traffic in Manhattan. These strong measures reflect New York City’s dense and complex street environment and the policy emphasis on safety and minimizing disruption. 4.1.2 Technological Adaptability The main technical approaches of China and the United States in densely populated urban areas differ significantly. China's deployment emphasizes the vehicle-road cooperation model, using vehicle-to-everything (V2X) and smart infrastructure to enhance vehicle autonomy. These mechanisms reduce a lot of pressure on AV operating in complex traffic environments. In Beijing's Haidian District and Yizhuang pilot area, roadside sensors and 5G communication networks transmit real-time data to AVs, improving their perception of traffic and pedestrians (Luo, 2023). The Ministry of Transport has explicitly promoted the construction of "smart roads". AI cameras, IoT devices and high-precision maps are embedded on highways and city streets to support the operation of AV. This reduces the burden on on-board systems by providing redundancy and broader situational insights. However, due to the traffic complexity of high-density cities, test vehicles in Beijing and Shanghai are generally equipped with 8-12 lidars, combining millimeter-wave radars with cameras to improve the recognition accuracy of 18 complex traffic participants. For example, the Baidu Apollo RT6 model is equipped with 8 Lidars, covering 360° without blind spots (Gasgoo, 2022). Even in dense traffic and complex road geometry, China's self-driving taxis can rely on on-board sensors and "smart city" infrastructure. In contrast, most of the AV projects in densely populated cities in the United States follow the core of single-vehicle intelligence, relying on on-board sensors and AI algorithms to achieve complex environmental perception. In San Francisco, Waymo and Cruise vehicles rely mainly on lidar, radar, cameras and on-board artificial intelligence, and rarely rely on real-time input from infrastructure. For example, Waymo vehicles are equipped with 13 cameras, 4 lidars and 6 radars, and multi-sensor fusion is used to improve the recognition accuracy of dense targets such as pedestrians and non-motor vehicles. Tesla insists on a pure visual solution, optimizing the real-time decision-making ability of urban streets through the FSD (Full Self-Driving) system. Some American cities have piloted networked traffic lights or dedicated lanes, but these are only limited demonstrations. Chicago, for example, plans to install 10 connected intersections as a pilot to aid future AV applications (CDOT, 2021). The technology stack of AVs in American cities is basically self-sufficient and capable of driving on unpredictable city streets. One reason is the lack of ubiquitous V2X deployment in the United States; another reason is that regulators prefer technology-neutral infrastructure. As a result, China's densely populated cities tend to favor the vehicle-road cooperation model, while American cities rely on highly automated vehicles that can handle densely populated 19 environments with only onboard systems. The Chinese approach may be able to scale faster in complex areas by reducing the cost per vehicle and improving safety through network monitoring. The American approach prioritizes innovation in vehicle artificial intelligence, which has been proven in California's rigorous testing system, but its large-scale deployment may be slow if the supporting infrastructure is lacking. 4.1.3 Urban Density and Development Impacts In these densely populated cities, the introduction of AVs has already begun to influence travel behavior and urban planning, although the potential has not yet been fully developed and utilized. AV are being regarded as an integral part of smart city projects by policymakers in China's mega-cities. They believe that AV can be useful in improving traffic congestion and reducing private car ownership in city centers. Moreover, AV should be used as a supplement to public transportation rather than a substitute at this stage (Li, 2022). For example, in Guangzhou, 50 autonomous buses are deployed on 10 fixed routes connecting major transportation hubs such as railway stations and airports; these routes have served more than 1 million passengers before mid-2023 (Ministry of Transport of the People’s Republic of China, 2024). Travelers are willing to incorporate autonomous shuttles into their daily transportation. In Wuhan, Baidu's Apollo Go autonomous taxis have 500 vehicles, about 1% of the city's total taxi amount (Feng, 2024). They are so popular that human taxi drivers have even launched a petition to limit their number. In densely populated Chinese cities, people are undergoing a gentle shift in travel patterns and are not averse to AVs. Beijing’s draft 2023 AV regulations 20 even seek feedback on using self-driving cars for urban mobility options such as car rentals and ride-hailing, suggesting planners are actively considering how to integrate shared AV fleets into the urban fabric. In the United States, densely populated urban centers have been more cautious about integrating AVs, so the visible impact on cities has been limited so far. In San Francisco, Waymo and Cruise AVs, as of 2025, this service still accounts for only a very small part of the city's overall travel. Due to the extremely complex traffic environment caused by urban density, the problem of AVs stopping unexpectedly often occurs. For example, parking near the Vice President Harris warning area and blocking traffic during a music festival (Police1, 2024). The cruise was also revoked due to frequent accidents, including dragging pedestrians. In 2024, it laid off 50% of its employees and turned to L3 assisted driving research and development, resulting in its Robotaxi service almost withdrawing from the market, further weakening the coverage of autonomous driving in San Francisco (Hawkins, 2024). The reliability of autonomous driving is doubtful, so people are calling on city officials to adjust how and where AVs operate. In addition to these early operational issues, land use or urban form in San Francisco and New York City have not yet changed significantly due to AVs. Despite this, urban planners have not given up studying future scenarios for the popularization of AVs (Silva, 2022). Depending on the deployment direction, whether the popularization of AVs may exacerbate urban sprawl or may also adapt to higher urban density. If AVs are primarily used as private transportation, reducing the cost of commuting, this could lead to increased urban sprawl, as people may be willing to live farther from work centers (Booth, 2024). In other case, assuming AVs are deployed as robotaxis, the number of private cars and parking needs in cities could 21 decrease, which could promote denser development in urban cores and more pedestrian- friendly streets over time (Li, 2025). Currently, US cities are in the early stages of pilot projects and have not yet made major infrastructure construction or zoning adjustments for AVs. New York City explicitly positions its emerging AV program as integrating AVs into existing urban safety and transportation frameworks rather than as a catalyst for reshaping the city. 4.2 Intermediate Density Areas (Suzhou, Chengdu vs. Pittsburgh, Chicago) For the intermediate density areas, I select Suzhou, Chengdu from China and Pittsburgh, Chicago from United State as the case study. Intermediate Density Areas are composed of continuous 1 square kilometer grid units, each with a population density of ≥300 people/km², and the total population of the agglomeration is between 5,000 and 50,000 people. However, the entire urban area does not fully meet the density and coherence of the "City Center". City (core district) Average Population Density (per km²) Total Population (2020) Source Suzhou 2,100 12.3 million City Population Chengdu Core: 6,200 Rural: 1,000 20.9 million City Population Pittsburgh Core:2,100 Rural: < 1,200 0.23 million U.S. Census Bureau Chicago Core: 4,600 Rural: 1,200 0.94 million U.S. Census Bureau Table 5.2: Population Density of Selected Cities in Intermediate 22 Chengdu and Suzhou have large urban and suburban structures, but the population and building density is a multi-center distribution with high core urban areas and medium and low peripheral areas. Since large industrial areas, open new areas, and satellite towns have not formed a complete ultra-high-density continuous belt, they should be classified as intermediate urban areas. The density of the core district of Pittsburgh and Chicago meets the standard of the “City Center”, but they should be classified as “Intermediate Density Areas”as the suburbs are less dense and not closely integrated with core district. Medium-density cities offer a different context for the deployment of AVs. In these settings, where urban forms consist of dense city centers and sprawling suburbs, policy approaches often need to balance innovation with local needs. 4.2.1 Policy Environment China's intermediate density cities are actively participating in the national autonomous driving program and often establish themselves as innovation centers to attract investment. Secondly, cities implement policy directives by building advanced infrastructure. After the national government launched the "intelligent vehicle infrastructure integration" pilot project, Suzhou actively responded and took advantage. In 2023, Suzhou opened China's first smart highway designed specifically for AV applications and equipped with holographic perception technology. Real-time health monitoring and traffic anomaly detection are achieved through distributed 23 fiber optic sensing, Lidar and other equipment, providing high-precision perception support for AVs (Chen, 2023). The Suzhou Municipal Government has also set up AV pilot areas in different areas such as some tourist areas, such as Jinji Lake, and high-speed rail new towns, in order to test autonomous shuttles and logistics delivery vehicles. The pilot covers more than 100 application scenarios such as smart travel, freight, and sanitation. Municipal authorities attach great importance to the pilot project and therefore receive support from local subsidies and partnerships (People.cn, 2022). In 2024, its intelligent vehicle networking industry will reach a scale of 45.14 billion yuan, gathering nearly 600 companies (Suzhou Municipal People’s Government, 2024). Chengdu, the capital of Sichuan Province, also launched a self- driving taxi pilot in its high-tech industrial park in 2022. The Chengdu Municipal Government initially deployed 8 Apollo Go cars in an area of 10 square kilometers and allowed Baidu to provide online taxi services to the public during daytime. Chengdu has incorporated autonomous driving into the smart community planning of the suburban "Future Science City" to promote the integration of vehicles, roads and clouds. For example, in cooperation with telecommute operators to improve 5G vehicle networking facilities, 16 L4 Robotaxi put into operation in Longquanyi District provide free services on two routes with a total length of 30 kilometer (People’s Daily Online, 2023). This is consistent with Chengdu's broader urban vision, which clearly regards AVs as part of the blueprint for high-tech sustainable communities. In all these cases, the policy means of China's medium-sized cities include the establishment of special zones, public-private partnership pilot projects, and the inclusion of AVs in urban development plans (People’s Daily Online, 2023). By 2024, China has even expanded the pilot project to 20 cities (many of which are second-tier cities, including Suzhou, Chengdu, Wuhan, 24 etc.) to promote the construction of standardized autonomous driving infrastructure and cloud platforms (Zhang, 2024). The pilot requires the integration of vehicles, roads, cloud computing and other technologies, and the exploration of commercial operation models to build standardized AV infrastructure and AV operation models. This ensures that cities such as Suzhou and Chengdu develop in sync with national standards while conducting local pilots. In the United States, cities with medium population density have taken a more decentralized and exploratory policy approach. Pittsburgh is a notable example. Pittsburgh's leadership hopes to promote local economic development by introducing high-tech and actively supported AV testing in the mid-2010s without federal involvement. In 2016, as one of the first cities in the United States to cooperate with the city government and companies in autonomous driving, Pittsburgh cooperated with Uber's Advanced Technology Group to allow Uber's AVs to be tested on Pittsburgh streets accompanied by safety drivers (BBC, 2016). Pittsburgh was therefore designated as an AV testing site by the U.S. Department of Transportation and has attracted a number of AV startups and research centers. Many mid-sized cities in the United States often lack coherent AV pilot policy goals and are not connected to large-scale transportation planning (McAslan, 2021). Pittsburgh's early AV testing was not closely integrated with public transportation or transportation goals, and there were some accidents, so some people criticized the city for conducting experiments privately without clear public interests (SCIAM, 2017). It has since enacted AV testing regulations and participated in state government initiatives. Pennsylvania has supplemented its then-incomplete policies with new guidelines and voluntary safety commitments. Chicago's approach is more cautious. Chicago’s 25 2020 Transportation Strategic Plan calls for exploring AV pilots and installing connected vehicle infrastructure at some intersections, but concrete deployment efforts have been minimal to date (CDOT, 2021). Chicago did approve a limited delivery robot pilot and is considering autonomous shuttles for specialized uses like running on dedicated lanes to and from O’Hare Airport, but these are still in the proposal stage (CMAP, 2019). In general, mid-sized cities in the U.S. are taking a more relaxed approach to policy tools— forming working groups, issuing guidelines, and collaborating on small pilots—rather than taking a prescriptive, mandatory approach like China. This difference reflects resource levels and risk tolerance. A city like Pittsburgh can relatively quickly approve AV trials by private companies but scaling it up to a comprehensive citywide service requires state support and coordination with public transit agencies, which is still in its infancy. 4.2.2 Technological Adaptability In both countries, intermediate density cities are proving grounds for perfecting autonomous driving technology, but the balance between vehicle capabilities and infrastructure support differs. The way China’s second-tier cities adopt autonomous driving technology is often promoted as part of smart city upgrades. Cities such as Suzhou and Chengdu follow the national model and place a high priority on infrastructure-enabled autonomous driving. For example, Suzhou’s smart highways create a controlled environment where connected AVs (CAVs) can receive high-fidelity data from the road, such as real-time traffic conditions and impending 26 hazards (Gasgoo, 2023). A favored technology path is for infrastructure upgrades to precede or accompany the rollout of new technologies for AVs themselves, ensuring that AVs can operate with the help of intelligent traffic management systems even outside of densely populated metropolitan areas. In addition, given the industrial characteristics of these cities, China’s mid- sized cities often focus on logistics and freight AV. For example, in eastern China, Zhoushan, a port city slightly smaller than Suzhou, has launched a pilot for autonomous trucks at its port terminal, while other cities such as Chongqing’s Yongchuan District are testing L4 autonomous trucks on 20 square kilometers of roads (CMRA, 2024) (Xinhuanews, 2024). As an industrial center itself, Suzhou is likely to benefit from autonomous freight transportation on its newly built smart highways. From a technical perspective, this suggests that vehicle-to-infrastructure (V2I) communications and cloud coordination are integral to China’s AV systems in a medium- sized environment – AVs are designed to be part of a network, whether carrying passengers or cargo. The Chengdu pilot project, while starting with basic self-driving taxis, coincides with Baidu’s efforts to build a 5G-enabled “intelligent driving project” in the city that aims to eventually support both self-driving buses and self-driving taxis through a central cloud control platform (Spencer, 2021). 27 Figure 1 Smart Highway in Suzhou (source: cnbeta) In the United States, autonomous technology deployment in medium-density cities has been more independent and with relatively limited driver requirements. Pittsburgh's trials primarily involved test vehicles equipped with advanced onboard kit that can map the city's streets. Pittsburgh's hilly terrain and seasonal weather conditions provide an ideal testing environment for AVs to validate technology and help improve vehicle software, but there is little use of the infrastructure that is available in Chinese cities (Pennsylvania Autonomous Vehicle Policy Task Force, 2016). During Uber's years of testing, no special sensors were installed on Pittsburgh's roads. Instead, the city used existing traffic control systems, with the city government providing traffic signal data to testers (Patel,2016). Chicago and its surrounding areas have a strong freight industry, and we have also seen some autonomous technology for truck transportation. Some companies have tested semi-autonomous trucks on highways in Illinois, and nearby Ohio and Michigan have corridors for testing truck fleets. These projects use road connections, such 28 as some vehicle-to-vehicle (V2V) communication between trucks but are not as sophisticated as China's city-wide sensor networks (Wisniewski, 2019). In terms of passenger transportation, the application of American technology in medium-sized cities usually comes in the form of low-speed shuttles or online ride-hailing pilots on selected routes. For example, May Mobility already operates autonomous shuttle services in mid-sized urban centers such as Grand Rapids, Michigan, and Arlington, Texas, using onboard sensors and pre-set routes to travel in less busy areas. These shuttles typically travel at speeds of 25-35 mph and sometimes on fixed routes, so the technological advancement required is relatively small (May Mobility). Due to the lack of widespread V2X infrastructure in the United States, even in mid-sized cities, AV solutions are designed to operate independently, with remote monitoring as a backup (Zhang, 2025). We do see some interest in connectivity. A pilot connected intersection in Chicago will allow vehicles to receive signal phase timing information, which may be useful for future AV algorithms. But these initiatives are incremental. In short, mid-sized cities in the United States are testing the waters with standalone AV systems (from cars to shuttles), while Chinese cities are building integrated digital infrastructure from the ground up to support AVs. 4.2.3 Urban Density and Development Impacts The deployment of AVs in intermediate density areas has not yet produced a clear effect, but the impact of density can be analyzed through early planning work. To enhance connectivity and controllable growth, China’s intermediate density cities integrate AV projects into their long-term urban development strategies. Chengdu and Suzhou treats AV industry to improve 29 transportation connections instead of constructing another new road for human drivers, since their urban boundaries keep expanding. For example, some AV shuttles are deployed to the surrounding areas of Suzhou train station to connect the commercial and dwelling parcels. Land use may change as a result, making the supporting facilities in the area around the train station easy to reach without a private car. Similarly, Chengdu is integrating AVs into its high-tech development district. They have planned wide roads equipped with sensor systems, dedicated pickup/drop-off points for robotaxis, and mixed-use zoning that assumes on-demand ride services. These are evidence that AV mobility is being considered in the planning of new areas in China's medium-density cities. Planners expect self-driving vehicles to support the growth of mid-sized cities by connecting dispersed areas more efficiently and potentially reducing the need for private vehicles in new neighborhoods (Liu, 2024). On the U.S side, medium-sized cities have begun to incorporate AVinto their long-term mobility plans, but observable impacts are still limited to pilot areas. For example, although Pittsburgh's land use has not changed due to the presence of AV test vehicles and related businesses settled in the city, they have accumulated experience of the interaction between AV and pedestrians. Issues such as keeping safe bike lanes and preventing AVs from disrupting public transportation are of great concern to Pittsburgh residents (BikePGH, 2017). It has prompted local advocacy groups to require the deployment of AVs to be consistent with the concept of "people-oriented" street design, as described in NACTO's "Blueprint for Autonomous Urbanism". So, while nothing has changed on the ground yet, policy discussions in Pittsburgh are actively considering ways to ensure that AVs promote rather than harm urban 30 livability (e.g., using AV data to optimize traffic signal timing, or requiring AVs to use caution in mixed traffic). So far, the direct impact of AV on Chicago's urban form has not been significant, but from a regional perspective, if autonomous trucks become popular, their impact can be imagined - logistics hubs may need to be redesigned to accommodate autonomous loading, and highways may also add dedicated autonomous lanes, thus changing infrastructure investment priorities. For passenger travel, if Chicago deploys autonomous shuttles connecting suburbs to transit hubs, it could attract more people living around, because people can take an autonomous shuttle for the last mile. Conversely, improved door-to-door autonomous ride services could encourage some people to live in more suburban or exurban areas, as such cars provide them with convenient access to work in distant city centers. One comparative study found that about 30% of American drivers might consider moving farther away if they had an autonomous car, compared with 42% in China (Guan, 2021). Urban sprawl caused by AVs may be a concern for both countries, but it may be more prominent in China's rapidly growing cities. In intermediate cities in the United States, where car dependence is already high, affordable autonomous commuting options could indeed expand the commuter base. As a result, some American urban planners warn that without policy intervention (such as congestion pricing or land use regulation), AVs may encourage suburban expansion—a continuation of the sprawl trend—rather than concentration. In summary, Chinese mid-sized cities are actively integrating AV into new urban developments, aiming to guide development and travel behavior to facilitate interconnected and efficient travel, while cities of similar size in the United States are still in the experimental stage, which may have an impact on spatial structure. 31 4.3 Low-Density and Rural Settings Next, I compare AV programs in low-density and rural areas in China and the United States, focusing on how sparse environments affect deployment goals, feasibility, and urban development outcomes. The experience of small Chinese cities such as Yangquan with US examples such as suburban Phoenix and rural towns are compared. The economic considerations and social needs of low-density areas are very different from those of megacities—reducing the incentives for infrastructure-intensive vehicle-to-everything (V2X) systems while increasing the importance of vehicle-orientated AV technologies and specific use cases. 4.3.1 Policy and Technological Adaption Yangquan, the smallest city in Shanxi Province, has begun adopting various autonomous driving services including robotaxi and self-driving buses despite their relatively low population density (People’s Daily Online, 2025). This reflects China’s top-down strategy to actively include smaller cities in national autonomous driving pilot projects. The national policy encourages the construction of intelligent transportation infrastructure across the country, so Yangquan and dozens of other cities have established autonomous driving test areas and upgraded smart roads with government support. In fact, even in areas with lower population density, local governments have worked with technology companies to deploy autonomous shuttles, Robotaxi and delivery robots in protected scenarios. Baidu has even deployed Apollo 32 in Yangquan. These pilot projects often include building V2X on key sections of roads - for example, Yangquan’s network of connected roads can enable real-time traffic monitoring and management, thereby improving traffic safety and relieving traffic congestion. However, when constructing comprehensive intelligent infrastructure for AVs outside of major urban centers, it is unfavorable from an economic perspective. The sparse traffic and vast geographical area make expensive sensor networks and 5G coverage difficult to achieve (Ansarinejad, 2025). While China’s national strategy prioritizes the interconnection of densely populated cities, in areas with lower population density, it relies more on strong on-board autonomous driving technology, just like the US strategy. The Yangquan’s application model embodies a hybrid approach, with limited V2X infrastructure installed at strategic locations funded by the central government, while the AVs themselves are equipped to handle most of the perception and decision-making independently (CRSA, 2022). This vehicle-orientated adjustment is necessary because achieving truly ubiquitous "smart road" coverage in rural areas will be costly even in China. Nevertheless, government support ensures that smaller cities can experiment with AVs as a tool for local development and improved public services. Policy directives such as the 2023 inter-ministerial notice on intelligent connected vehicles have also opened the door to L3/L4 autonomous driving pilots in many high- and low-density cities. In short, China's high- level commitment has enabled the deployment of AVs even in areas with lower population density, although the scale of infrastructure investment will be adjusted according to local needs (McKinsey&Company, 2023). In the United States, AV deployment in low-density and rural areas is driven primarily by 33 private sector initiatives and state-level policies. Unlike China’s top-down strategies, U.S.’s strategies are bottom-up and vehicle-focused. Instead of blanketing highways or suburbs with sensors and dedicated communications systems, U.S. companies are investing in developing advanced onboard Lidar, cameras, mapping, and AI to enable AVs to navigate existing roads independently. The vehicle-led approach to autonomous driving fits the U.S. situation, where AVs typically navigate highways and suburban streets with simple traffic conditions without the need for new roadside infrastructure. Waymo's robotaxi service in suburban Phoenix, for example, covers a wide swath of low-density neighborhoods without requiring special road modifications; the vehicles rely on their own suite of sensors to navigate wide arterial and dead- end streets (Marshall, 2018). The Phoenix metropolitan area, known for its wide streets and pleasant weather, became an early AV hub precisely because its low-density suburban form reduces complications such as pedestrian traffic congestion (Marshall, 2018). In fact, Waymo has been expanding its operations in the Phoenix area to serve car-dependent communities, viewing suburban sprawl as an opportunity for AV ride-hailing services. Early deployments have focused on use cases where existing technology is feasible and where there is a clear private benefit, such as autonomous highway functionality and autonomous trucking between logistics hubs. Several companies are already piloting autonomous trucking on interstate highways in the Southwest, taking advantage of the fact that nearly half of U.S. truck miles are spread out on rural roads and interstates (Zarlf, Starks, Sussman & Kukreja, 2021). These trials use standard roads with minimal modification, highlighting a vehicle-orientated approach. In summary, the U.S. approach in low-density areas is characterized by the adaptive reuse of existing automotive infrastructure and a policy environment that allows autonomous innovators 34 to operate on public roads with few special arrangements. The downside of this laissez-faire approach is that without public sector investment in connectivity, AV deployment in rural areas must overcome challenges such as spotty wireless network coverage and poorly maintained roads on their own. 4.3.2 Impacts of Low Urban Density on AV deployment Next, I compare AV programs in low-density and rural areas in China and the United States, focusing on how sparse environments affect deployment goals, feasibility, and urban development outcomes. We contrast the experience of small Chinese cities such as Yangquan with US cases such as suburban Phoenix and rural towns. Unlike megacities, where economic considerations and social needs are different, low-density areas reduce the incentives for infrastructure-intensive vehicle-to-everything (V2X) systems, while increasing the importance of vehicle-focus AV technologies and specific use cases. Perhaps the most significant impact of low urban density on autonomous driving technology is the push-back against infrastructure-intensive solutions, which in turn will shift to vehicle- focus autonomous driving. Chinese policymakers have proposed using V2X communications, smart traffic signals, and cloud-based coordination to manage the huge number of vehicles in densely populated mega-cities. But in rural areas or small towns, the return on such infrastructure is lower. Fewer vehicles and less traffic congestion make infrastructure economically and functionally unnecessary. Low-density environments are economically 35 unable to build and maintain extensive intelligent road networks for a small number of vehicles. Researchers point out that remote locations make the development of fully connected "smart cities" more difficult, and sparsely populated areas often face connectivity barriers because cellular networks are unstable and far away, thus hindering V2X communications and real-time data sharing in rural areas (Ansarinejad, 2025). However, in the United States, this shift will not cause much trouble because from the beginning, its AV industry has assumed the hardware of the vehicle itself is the primary solution (AVIA, 2025). Considering that people cannot rely on external networked navigation on distant rural roads, automakers have equipped cars with high-tech sensors and high-definition maps helping them to interpret road conditions in real time. China's experience also reflects this trend. Cities like Yangquan do not yet have smart road infrastructure that supports the operation of AVs, and they still rely on their own hardware for daily operations. In low-density urban environments, both countries tend to prefer similar technical solutions. They both believe that highly AVs can cope with imperfect roads, unmarked country roads, or random hazards without continuous V2X input (USDOT, 2021). At the same time, safety and reliability technologies play an important role in future development. They need to be equipped with powerful sensors and reliable performance in all- weather operation to operate safely in curving or twisting roads. In rural pilots, engineers found that vehicle sensors encountered challenges such as faded lane markings, gravel roads, and strong sunlight glare (Marketplace, 2024). Solving these problems with more advanced on- board processing technology, such as improved vision algorithms or sensor fusion, instead of installing new road infrastructure on every section is more feasible from economic perspective. Therefore, from a qualitative perspective, low-density environments are more inclined to carry 36 intelligent AVs. U.S. policymakers have supported this approach by withholding funding for roadside unit projects, while the Chinese government has admitted this by supporting projects that combine some infrastructure with strong vehicle AI in less populated areas, rather than just infrastructure. Despite differences in top-down and bottom-up philosophies between the two countries, both countries’ deployment of AVs outside of large cities will inevitably tend toward vehicle-focus autonomy. 5. Summary Table Urban Density China United States Densely Populated Areas National strategies promote large- scale pilot projects, Vehicle to Everything (V2X) + smart roads, AV as a supplement to public transportation and reduce reliance on private cars Local decentralization (California allows testing, New York strictly restricts); Waymo/Cruise many problems in the experimental stage, no significant change in urban form Intermediate Density Areas National pilot extended to second- tier cities (Suzhou/Chengdu); Smart infrastructure first and logistics scenarios first; New urban planning integrates AVs to optimize transportation connections Small-scale testing led by local governments (Pittsburgh/Chicago); independent vehicle-mounted system + low-speed shuttle bus; concerns about conflicts between AVs and pedestrians, no significant changes in form. Low Density and Rural Areas National pilot projects in remote areas (Yangquan); selective V2X + strong in-vehicle AI; improving traffic accessibility may aggravate the urban-rural gap Mainly led by private companies(Phoenix suburbs); completely dependent on vehicle sensors; suburban services expand commuter range, potential urban sprawl risk Table 6.1 summary table 6. Discussion As the initially hypothesized, urban density was the primary variable influencing the 37 adoption and impact of autonomous vehicles (AVs). However, further research revealed that, regardless of density, institutional structures and governance models play a more prominent role in shaping AV development than density itself. As the initially hypothesized, urban density was the primary variable influencing the adoption and impact of autonomous vehicles (AVs). However, further research revealed that, regardless of density, institutional structures and governance models play a more prominent role in shaping AV development than density itself. In China, a centralized planning system has enabled rapid deployment of AV technology through coordinated pilot zones, standardized technical frameworks, and direct infrastructure investment. Furthermore, China's AV deployment policies allow the government to shape industry development through public-private partnerships and subsidies. National support has enabled local governments to implement AV-related initiatives on a sustained and large scale, as demonstrated in medium-density cities such as Suzhou. In contrast, the United States, with its federal system, has decentralized AV regulation across state and municipal governments. Private companies in the United States often lead innovation in AV technology. This model, both directly and indirectly, has led to uneven AV deployment, with some cities experiencing rapid development due to lax state laws, while others face public resistance and regulatory ambiguity due to historical and social factors. 38 7. Conclusion By a detailed comparative case studies of cities in China and the United States, I systematically analyze how urban density affects the deployment of AVs. With the application of SCOT theory and the Policy-Technology-Density framework, there are qualitative differences in AV industry development path between different urban densities. This study demonstrates that rather than a basic condition, urban density is actually a determinant of AV integration or deployment. The comparative case study between China and the United State shows that the density fundamentally shapes policy priorities and technology development direction. The complex transportation and spatial constraints of densely populated areas require strong technical and policy interventions. Chinese cities have adopted an infrastructure-supported approach, including extensive V2X networks and vehicle-road- cloud systems to assist AVs to make up for the lack of single-vehicle capabilities, while US cities tend to rely on advanced on-board sensors and artificial intelligence to construct self- sufficient AV systems in the absence of pervasive infrastructure. Despite their different governance actions, both countries demonstrate that high-density urban forms require proactive integration measures to ensure that AV enhance rather than disrupt urban mobility. Chinese intermediate cities have actively integrated AV pilot projects into new urban development plans to promote efficient and fit-in mobility gaps, while similar-sized US cities are still in the experimental stage of AV testing. Due to the lack of strategic planning, the 39 latter may miss the opportunity to shape urban development in the new era. Therefore, the situation of intermediate cities dealing with further highlight the impact of density. Finally, in low-density and rural areas, the analysis of the two countries found convergence in approach. The sparse population and vast geographical area make large-scale infrastructure investment impractical and uneconomical, and both countries have shifted their focus to vehicle-focus solutions. In these areas, due to the limited returns of large-scale smart road systems, the deployment of AVs is usually with strong on-board autonomy. Overall, the main findings confirm that urban density significantly affects traffic patterns and deployment feasibility, determining which AV technologies and policies are most effective in each context. Policymakers may face unintended consequences when density is not properly considered. AVs may exacerbate suburban sprawl rather than improve urban efficiency if they are left to free market forces. However, urban density, as a single explanatory variable, has significant limitations in its ability to explain observed differences in AV development outcomes. Even in cities with similar population density parameters, such as New York City and Shanghai, the development trajectories and maturity of autonomous vehicles can exhibit significant divergence. These differences stem not only from the profound influence of urban spatial structural attributes such as density distribution and road network form, but also crucially from differences in governance models embedded in specific social systems, deeply embedded cultural contexts, and differentiated policy orientations and strategic intentions. Future research needs to adopt a multidimensional analytical model that encompasses not only density, policy instruments, and technology fit, but also the broader institutional context. 40 8. Policy Recommendations Densely populated cities should leverage autonomous driving technology to enhance public transportation rather than simply make it become substitutes. Priority should be given to integrating AVs into high-density areas, enabling them to supplement public transportation and alleviate congestion in congested urban cores. There are three interconnected measures can optimize system efficiency: 1) Designated lanes with dynamic capacity allocation for autonomous shuttles during peak hours; 2) Adaptive traffic signals utilizing vehicle-to- infrastructure communication to break the wall; 3) Digitally managed micro-zones for passenger transfers that minimize curbside conflicts. Investing in connected vehicle infrastructure, such as connected intersections and 5G corridors, can improve safety and navigation capabilities in these complex environments. At the same time, regulations should limit the unrestricted use of private AVs in densely populated downtown areas, such as through congestion pricing or additional charges for zero-occupancy vehicles. Intermediate cities have an opportunity to consider AVs as they shape growth patterns. Cities should carefully develop these technologies so that they promote sustainable development, rather than undermine it. They can encourage proactive planning and pilot projects to integrate AVs into evolving urban development and transportation networks. With growing populations, urban planners should incorporate AV-friendly designs into new districts and redevelopment projects, such as smart parking management and dedicated drop-off areas. Public-private 41 partnerships can be established to test AV buses or shuttles as feeders to public transportation which improve “first-last-mile” connectivity. Policymakers should also use this modest-scale opportunity to guide travel behavior. Shared AV mobility services should be promoted rather than private AVs to prevent traffic congestion and suburban sprawl. Land use and zoning policies in these cities could be updated to support mixed-use, transit-oriented development models that leverage AVs for accessibility. The strategy for low-density areas is to rely on the technological capabilities of vehicles and selective public investment to achieve the benefits of AV access and safety improvements. They should focus on pragmatic deployment of AVs to address long-distance and sparse demand while avoiding expensive infrastructure investments. For suburban, exurban, and rural communities, the deployment of semi-AVs that can operate on traditional road networks is a practical solution. Policy frameworks should prioritize the expansion of shared AV services and address mobility issues for the elderly residents living in distant areas through targeted subsidies or rural transportation grants. Infrastructure transformation requires selective rather than comprehensive modernization, with upgrading cellular network connections on major routes and improving digital maps of key corridors to fully support navigation systems. At the same time, safety certification must continue to evolve to address challenges unique to rural areas, such as navigating unpaved roads and irregular traffic patterns. Land use planning needs to be proactively adjusted to prevent urban sprawl—even though the convenience of automated “door-to-door” travel may increase, zoning regulations need to be revised to maintain development density thresholds. 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