## 6 Simulation and Verification of Operation Procedure in Apron U-Shaped Area
### Experimental Results and Comparative Analysis  
#### 6.2.1 Comparison of Different Indices of U-Shaped Area  
Based on the time-constrained apron operation simulation model constructed, a computer simulation capacity evaluation method was used to evaluate the apron U-shaped area operation capacity corresponding to the three types of operation procedures. The capacity of the U-shaped area for the exclusive, partition-shared and global-shared operation procedures is 52, 58, and 61 aircraft per hour, respectively. It can be seen that the global-shared operation procedure can increase the apron capacity by 14.8% and 5.0% compared to the exclusive and partition-shared operation procedures, respectively. We calculate the flight flow and indices of Wuhan Airport for a particular day based on the real operational data of the airport and record them in Figure 9, which shows the results of the relationship analysis between flight flow and different indices under different U-shaped area operation procedures. It can be seen that when the flight flow rate is less than 30 aircraft per hour, i.e., when the capacity and flow ratios of the exclusive, partition-shared and global-shared operation procedures are less than 57.7%, 51.7%, and 49.2%, respectively, the difference in the number of conflicts occurring under the three operation procedures is small, and the degree of mutual interference between aircraft on the apron is low. As the flight flow rate increased, the capacity and flow ratio of each operation procedure increased, and the difference in the conflict probability of the three operation procedures gradually became obvious. The conflict probability for all three types of operation procedures increased, with 34.6%, 32.4%, and 24.9% for exclusive, partition-shared, and global-shared operation procedures, respectively. The increase in conflict probability was more pronounced for the exclusive operation procedure and the partition-shared operation procedure than for the global-shared operation procedure. As for the analysis results of the relationship between flight flow and conflict resolution time under different U-shaped area operation procedures, we note that when the flight flow rate is less than 25 vehicles/h, i.e., when the capacity ratios of the exclusive, partition-shared, and global-shared operation procedures are less than 48.1%, 43.1%, and 41.0%, respectively, the difference in the conflict resolution time of the three operating procedures is small. The increase in conflict resolution time for the three operation procedures is 1754.5 s, 6430 s, and 8260 s, respectively, and the increase in conflict resolution time for the global-shared operation procedure is more moderate compared with the other two operation procedures. The reason for this is that when the traffic volume exceeds a critical value, the interaction between aircraft deepens, and due to the strict limitations of the exclusive operation procedure, the total number of waits and the total time spent at the U-shaped area entrance are bound to increase as the traffic volume continues to increase, which inevitably leads to local congestion on the apron system. In contrast, the global-shared operation procedure is less restrictive and can be dynamically adjusted according to the flight flow, so the conflict probability and conflict resolution time are less affected by the flight flow and the operation efficiency is higher. In terms of the resource use efficiency indices, when the flight flow is small, there is no difference in the average maximum traffic volume corresponding to the three operation procedures (e.g., when the flight flow is 20 vehicles/h). When the flight flow is  
Figure 9: Relationship between Flight Quantities and Different Indices Using Different Operation Procedures. Procedures.