The implementation of shared parking program can effectively increase the utilization rate of existing parking space resources. At present, shared parking program has not been widely practiced in China, and the prerequisite for this prospect to be implemented is whether the private parking space owner group can quickly and widely accept shared parking program. In this study, considering the differences in the economic development, urban planning, and parking pressure in cities of different levels, the theory of planned behavior and the benefit-risk perception model (C-TPB-BRA) are combined as the theoretical framework to explore the intention to share parking space from the perspective of the owners of private parking spaces in cities of different levels. Based on China’s empirical data, structural equation models are built to verify the hypotheses proposed. Our results show that (a) the intention of private parking space owners in different levels of cities to participate in shared parking and the mechanism of action of the psychological factors are different, and not all psychological factors have a direct impact on the intention to share. In first-tier, second-tier, and third-tier cities, Subjective Norm (SN) and Perceived Behavioral Control (PBC) indirectly affect Behavior Intention (BI) through Attitude (ATT), Perceived Benefit (PB), and Perceived Risk (PR). In the fourth-tier cities, SN and PBC directly affect BI. Except for BI, other psychological factors influence each other significantly; (b) the psychological factors affecting the intention to supply shared parking spaces in first-tier, second-tier, third-tier, and fourth-tier cities, respectively, are PB > ATT > PR, PB > PR > ATT, PB > PR > ATT, and PB > SN > PBC > ATT > PR. Our research results could help determine the internal factors that affect the intention of parking space suppliers and their mechanisms of action to participate in shared parking, and on that basis, our findings could also help governments and platform operators to promote shared parking development plans.
In recent years, the economy has developed rapidly and the number of motor vehicles has increased greatly, but the infrastructure construction and management level have not been correspondingly improved, so the contradiction between supply and demand of parking has become increasingly prominent. In addition, according to relevant statistics , in the context of sudden public health incidents such as the COVID-19, citizens are more concerned about the hygiene of public transportation and shared bicycles, resulting in a further reduction in the proportion of public transport trips, and the proportion of private car trips increased, which will further intensify parking needs.
In addition, Amott  pointed out that, in Boston and some major European cities, more than 50% of cars need to find parking spaces during peak hours. The research of Shoup  pointed out that if each parking activity requires three minutes to find a parking spot, the cruising mileage of each vehicle needs to be increased by about 1825 kilometers per year. Besides, the lack of parking spaces can also lead to illegal parking activity, increased time costs caused by queuing and waiting, etc., thereby exacerbating carbon dioxide emissions . This situation is more serious in many cities in China. Zhao et al.  constructed a quantitative model to evaluate the emission reduction effect of the implementation of the shared parking policy. The results show that 120 shared parking spaces in Beijing can reduce about 400 tons of carbon dioxide emissions a year; if 20% of the existing parking spaces in Beijing are shared, every year carbon dioxide emissions can be reduced by up to 7.3 million tons. Ayala  found that more than 3.1 million gallons of gasoline was wasted and more than 48,000 tons of carbon dioxide was emitted due to the search for parking spaces in Chicago. Therefore, if the problem of parking difficulty can be solved, the parking pressure can be effectively alleviated, the driver’s time to find parking is greatly reduced, and the environmental pollution caused by vehicle emissions can be alleviated.
In addition to the contradiction between supply and demand of parking, another prominent manifestation of the current urban parking problem is the inefficient utilization of parking resources, which is mainly reflected in the imbalance in the space-time utilization of parking resources. For example, parking spaces in office areas are usually vacant at night and on weekends, while parking spaces in residential areas are often vacant during workdays during the day, which also provides an opportunity to meet parking demand without the need to build more parking lots . According to relevant statistics, 485,000 parking spaces in Hong Kong are designated for private use, accounting for nearly 70% of the total number of parking spaces; Beijing’s residential parking resources account for 58.1% of all parking resources, during working hours nearly 800,000 private parking spaces have been left unused , and because most urban residents work inconsistently with their homes, parking spaces in residential areas have been unused during the day on weekdays. If the spare time of these private parking spaces can be used effectively, the parking problem can be greatly alleviated.
In recent years, the concept of shared parking has been proposed, the basic idea of which is that the parking space owner sells parking permits for the idle period of their parking spaces to public users on the electronic parking platform , and travelers with parking needs can purchase a parking permit through the parking platform. The relationship between supply and demand is shown in Figure 1. Some cities have already experimented with shared parking, but private parking space sharing in residential areas is still in its infancy. Most urban residents do not know much about shared parking in residential areas, and the number of users of each shared parking platform is small, so participation in shared parking is far from enough. Therefore, it is very important for urban planning and parking management to understand the decision-making mechanism for people to accept shared parking.