## 1 Introduction  
China has a large population base and particularly inadequate land resources. With the advancement of urbanization, the number of private cars continues to grow. According to statistics, the number of motor vehicles in the country is projected to reach 435 million in 2023, with 24.56 million newly registered cars, marking a 5.73% increase from 2022 [1]. As a result, most cities in China face varying degrees of traffic congestion. The fundamental reason is that the speed of road construction is far less than the growth rate of traffic demand, leading to an imbalance between traffic supply and demand. China is a mountainous country, and valley cities account for approximately half of the cities in China [2]. The term river-valley-type cities refers to cities that are formed and developed between valleys and rivers, such as Lanzhou and Xining. Due to the limitations of terrain and the division of the river, the road resources in river-valley-type cities are more limited than those in plain cities, making the contradiction between supply and demand particularly prominent. However, new roads alone cannot solve the urban traffic issue [3]. Park and Ride (P&R) is an effective method to reduce the number of private cars entering the city center by implementing a low-cost or even toll-free management policy to encourage motorists to transfer to the subway at the city's periphery bottleneck [4]. This helps to reduce travel costs and promotes environmental protection. However, it also faces some challenges, such as inconvenient transfers, reliance on the public transportation system, parking-lot management issues, and the possibility of worsening congestion near the stations. Therefore, when constructing Park and Ride facilities, it is necessary to balance their advantages and disadvantages and take corresponding measures according to the traffic environment of different cities to optimize the user experience of Park and Ride. The comparison between P&R and driving all the way is shown in Figure 1. In river-valley-type cities, P&R can not only alleviate the issue of car congestion and parking difficulty in the narrow junction between the urban groups and within the group center but also strengthen the connectivity of subway stations. This is one of the effective traffic management strategies to reduce urban carbon emissions and alleviate traffic pressure in the central area. In addition, the axial distance of transportation corridors in river-valley-type cities is long, which presents a clear agglomeration effect that is highly beneficial for the development of subways [5]. Commuter travel, as the primary travel demand in urban transportation, reflects the efficiency of urban travel. Therefore, it is of great significance to study the commuting behavior of motorists who use P&R in river-valley-type cities to alleviate traffic congestion issues in such areas. P&R has been successfully applied in London, Singapore, Tokyo, Shanghai, and other cities, but some cities have failed [6]. This highlights the importance of adjusting P&R based on the requirements of motorists in various traffic environments, particularly in river-valley-type cities, which differ significantly from plain cities in terms of terrain, spatial layout, and road network planning and development. The purpose of this paper is to identify the factors that influence various aspects of motorists' behavior of using P&R in a river-valley-type city and to assess the extent of their impact. We conducted a questionnaire survey in Lanzhou and analyzed the collected data using the structural equation model (SEM) and the Logit model. The results of this study could offer valuable insights for accurately formulating traffic policies and optimizing the P&R service environment to encourage motorists to embrace P&R as a reliable mode of travel. It also helps to improve the use of P&R in river-valley-type cities and provides a certain degree of reference for other river-valley-type cities. This paper is mainly divided into five parts.