## 4 Results  
Aiming at the problem that there are significant differences in the utilization efficiency of parking spaces in different spatial locations of complex parking lots, this paper first constructed a parking spaces supply demand characteristics indexes system from the perspective of \"parking space level\", and then analyzed the demand utilization characteristics of parking spaces in different spatial locations, to accurately grasp the existing parking spaces utilization problems. On this basis, a model of the dynamic allocation of parking  
Figure 6: (**a**) Parking space turnover number after implementing dynamic allocation; (**b**) Parking space average parking time after implementing dynamic allocation; (**c**) Parking space total parking time after implementing dynamic allocation; (**d**) Parking space average interval time after implementing dynamic allocation.  
spaces was constructed to balance the parking spaces occupancy rate in different zones of the parking lot and improve the drivers' degree of satisfaction. The main conclusions are as follows:  
1. A parking spaces supply demand characteristics indexes system was constructed. The parking space spatial supply service level indexes include the distance between parking space and pedestrian entrance and exit (elevator, stairs), the distance between parking space and vehicle entrance and exit, and occupancy of parking spaces on both sides of parking space. The parking space demand characteristics indexes include parking space occupancy condition, turnover number, total parking time, average parking time and parking interval time. Metro City complex was taken as an example. The parking space demand characteristics indexes were calculated and visualized. The utilization status of parking spaces in different spatial-temporal locations in the parking lot was analyzed. Based on the above analysis result, the parking problems were judged in detail.
2. In order to balance the occupancy rate of parking spaces in different parking zones and improve drivers' satisfaction degree, a model of the dynamic allocation of parking spaces was constructed. Firstly, drivers' parking space choice preference was considered, the \"user optimal parking space\" was calculated. On this basis, the \"system optimal parking space\" is calculated by considering the occupancy rate of parking spaces in different parking zones.
3. A model of the dynamic allocation of parking spaces was simulated. The results show that after the dynamic allocation of parking spaces, the difference between the turnover numbers of parking spaces in zones A and B decreased from 2.24 times to 0.03 times. The difference in the total parking time between zones A and B decreased from 1.3 h to 0.6 h. The average interval time of parking spaces is small and evenly distributed. This suggests the model of the dynamic allocation of parking spaces can effectively improve the overall utilization efficiency of parking spaces and increase drivers' degree of satisfaction.  
Besides, the number of zones have an influence on the results. In the future, we can explore the optimal parking spaces allocation and effect evaluation under different parking zone conditions.  
The authors confirm that their contributions to the paper were as follows: study conception and design: [PERSON], J.C., K.L., C.Z.; data collection: K.L.; analysis and interpretation of results: [PERSON], J.C., K.L., C.Z.; draft manuscript preparation: G.Y. All authors have read and agreed to the published version of the manuscript.  
This research is supported by the National Natural Science Foundation of China (No. 71971059), the Key Project of Transportation Science and Technology Achievement and Transformation of Jiangsu Province (2019Z01) and the Fundamental Research Funds for the Central Universities (2242020R20026).  
Not applicable.  
The authors declare no conflict of interest.