## 4 Discussion  
Circuity functions as a metric for assessing the appeal of trip routes and is well suited for the analysis and comparison of cities and urban regions. The original concept of circuitry overlooks traffic patterns and flow, which are essential factors in assessing traffic efficiency. To address this issue, the circuity framework includes considerations of travel time and travel volume, leading to the subsequent introduction of transportation network travel speed and FWTC. These concepts are employed to assess the effectiveness of intercity traffic within urban clusters. Additionally, different from real-time traffic time, the transportation network travel speed and FWTC can effectively take into account the factor of travel distance, allowing for a comprehensive comparison and analysis of travel efficiency across various city pairs. In contrast, real-time traffic data solely facilitates comparing the efficiency of different traffic modes between the same city pair. Compared to original circuity, transportation network travel speed and FWTC not only better reflect the preference of the majority of riders, but also accommodate different travel modes. Original circuity uses route distance to calculate intercity travel efficiency, which leads to the same efficiency for travel paths with the same route distance, but different travel times taking varied transportation modes. This phenomenon is evidently unreasonable. The issue does not apply to transportation network travel speed and FWTC, because they use travel time to define efficiency. Therefore, with the rise of multimodal transportation, transportation network travel speed and FWTC are widely used. It is important to note that the transportation network travel speed, technologically rational traffic speeds, and real average travel speed of a transportation mode are related, but not equivalent. From the perspective of calculation method, transportation network travel speed is the ratio of the whole journey time to the European-style distance of OD, traffic speed is instantaneous values with the unit of distance traveled per unit time, while average travel speed represents the average traffic speed of the entire route. The essence of transportation network travel speed and FWTC is the time cost of travel, taking varied modes of transportation. Travel technology does not directly influence transportation network travel speed and FWTC. Instead, it affects transportation network travel speed and FWTC by influencing travel time. Generally speaking, modes of transportation with higher technologically rational traffic speed tend to complete the same displacement in shorter time durations. However, there are many factors affecting the travel time, such as the operating speed of each section, the layout of the transportation network, and the transfer time. These factors are taken into account by the transportation network travel speed and the FWTC. The transportation network's travel speed by automobile offers the advantage of increased connectivity within a 200 km radius, while also ensuring centralized data distribution. This phenomenon could be associated with varying proportions of HSR and conventional trains in different regions. In developing regions, intercity travel is predominantly facilitated by conventional trains, whereas developed regions have the option to utilize HSR for more efficient transportation. This discrepancy results in significant variations in travel speeds within the transportation network, despite covering the same Euclidean distance. Variations in travel speeds exist within transportation networks across various city clusters. The variations stem from the geographical separation of prefecture-level cities and the distinct developmental circumstances of transportation networks. Therefore, it is imperative to strategically determine the allocation of investment in transportation modes, based on the distances between prefecture-level cities within city clusters.