## 3 Results and Discussions
### Function-Cost Effectiveness Analysis of Collaborative Intelligent System  
Based on the function-cost effectiveness analysis model discussed in Section 2.4, combined with the statistical data on average usage intensity of different types of roads in Beijing, the forecast data for the future ownership of intelligent vehicles in Beijing [34], the costs of roadside intelligent infrastructure at different levels, and the levels of autonomous driving functions that can be achieved by the vehicle-road collaborative intelligent scheme, the function-cost effectiveness brought by different levels of intelligent transformation of different levels of highways can be obtained, as shown in Figure 15. From the perspective of function-cost effectiveness, the order of intelligent upgrading of highways is as follows: motorway, class-1 highway, class-2 highway, and class-3 highway. It is worth noting that the proposed model is a more general framework for the future ownership of intelligent vehicles.  
Figure 14: Distributed cost of intelligent scheme at roadside. (**a**) Highway. (**b**) Urban road.  
Figure 13: Life cycle cost of intelligent scheme at roadside.  
that, regardless of the type of road, since the primary intelligent infrastructure can only serve primary and intermediate autonomous driving, with future technology and industry shifting towards the development of advanced autonomous driving, the function-cost effectiveness of the primary intelligent infrastructure will decrease year by year. The roadside intelligent capabilities will also need to be upgraded to higher levels to match the development needs of vehicle-side intelligence. Among them, as a closed road, expressways have a simple traffic scenario, lower technical difficulty, and possess the highest function-cost effectiveness, making expressways a priority for intelligent upgrading pilots. In contrast, by deploying primary/intermediate intelligent infrastructure on class-3 highways, the functional benefits reflected on the vehicle side, even by 2050, will not be able to recoup the costs of roadside intelligent infrastructure. It is expected that after 2035, directly deploying advanced intelligent infrastructure on class-3 highways will gradually become function-cost effective, and class-3 highways can be considered the last objects to be intelligently upgraded in the urban road network.  
The results of the function-cost effectiveness brought by the intelligent transformation of different types of urban roads are shown in Figure 16. Overall, urban roads in Beijing have a higher function-cost effectiveness compared to highways. The order of intelligent upgrading of urban roads is as follows: urban expressways, urban main roads, and urban secondary roads. As semi-closed roads with relatively simple traffic scenarios, urban expressways have the smallest mileage scale and the highest function-cost effectiveness. They can be prioritized for intelligent upgrading on urban roads, and advanced intelligent schemes can be directly selected to support the demonstration and implementation of higher levels of autonomous driving, thereby achieving function-cost effectiveness. For main and secondary urban roads, the function-cost effectiveness of deploying primary or intermediate intelligent infrastructure is relatively low at the early stage of low penetration rates of ICVs. It is considered that with the improvement of the technical maturity of roadside intelligent schemes, the deployment of advanced intelligent roads on urban main and secondary roads can be completed after 2026 in sequence.  
Figure 15: Function-cost effectiveness analysis of collaborative intelligent system (highway).