## 5 Discussion  
The purpose of this study is to determine the various factors influencing P&R use in urban areas and to investigate how motorists' spatial perception of special terrains moderates the factors affecting P&R usage behavior in a river-valley-type city. Our research led to some interesting conclusions. According to the results of Model 1 and Model 2, motorists' driving age, degree of freedom in working time, ownership of private car, transportation payment, and the experience of using P&R have significant effects on motorists' P&R usage behavior in river-valley-type cities. Transportation costs paid by companies, including fuel and parking fees, serve as a significant disincentive for motorists to use P&R to commute [51]. Unlike some studies, monthly income does not have a significant effect on P&R usage behavior. We speculate that companies with higher-monthly-income motorists may offer higher transportation subsidies. Even with the use of P&R, there may not be a significant transportation fare gap to entice higher income motorists to transfer to P&R commuting. Compared with driving all the way, the time and cost saved by using P&R have a significant impact, which aligns with the findings of previous studies [11; 12; 13; 14]. In Model 1, gender has a significant effect on P&R use behavior. Women play a more important role in the family. Therefore, female motorists are more likely than men to choose P&R for commuting after dropping their children off at school. The peak period of river-valley-type cities is longer; motorists with less degree of freedom in working time and departure during peak hours will bear a greater risk of being late, so they are more inclined to commute by P&R [52]. Different from previous studies, we believe that more private car ownership reflects motorists' travel preferences to some extent, so they still choose to commute by car even in the terrain background of river-valley-type cities [33]. Due to the complex terrain of river-valley-type cities, motorists with a lower driving age obviously face higher driving pressure and turn to P&R commuting [29; 53]. Similarly, the experience of using P&R clearly has a significant impact on motorists' P&R usage behavior [29; 53]. Figure 5: (**a**) The moderating effect of terrain spatial perception on the distance between workplace and residence and P&R use behavior; (**b**) the moderating effect of terrain spatial perception on the river crossing demand and P&R use behavior; (**c**) the moderating effect of terrain spatial perception on the travel characteristics of group and P&R use behavior; (**d**) the moderating effect of terrain spatial perception on the departure time and P&R use behavior; (**e**) the moderating effect of terrain spatial perception on the time saved by using P&R and P&R use behavior; (**f**) the moderating effect of terrain spatial perception on the road slope between workplace and residence and P&R use behavior. The subjective and objective built environment proposed for river-valley-type cities in this paper has a significant positive impact on the motorists' use of P&R, which is also the part to be emphasized of our study. In cities of the same scale, river-valley-type cities exhibit a greater degree of separation between residence and workplace, steeper road slopes, and more distinct group characteristics. Additionally, there is an imbalance in traffic development between the outskirts and the center of the urban group. Moreover, rivers flow parallel to the main axis of the city. As a result, travelers using ground traffic mode in these cities will inevitably need to find bridges to cross the river, leading to longer detours. Therefore, motorists in river-valley-type cities are more inclined to choose P&R. As far as the security perception of motorists using P&R is concerned, parking spaces in river-valley-type cities are scarce, and motorists find it difficult to locate parking spots. Parking lots of P&R have comprehensive lighting and monitoring facilities, which enhance security for vehicles [54].