## 1 Introduction  
Valet parking technology is a service that can help people park their vehicles without any drivers' operation [1; 2]. It was born based on automatic parking [3; 4], and combines the advantages of automatic parking technology and driverless technology [5; 6; 7; 8]. The user only needs to drive the vehicle to the designated drop-off area of the parking lot. After getting off the vehicle, the vehicle will go to the designated parking space for parking. People do not need to find the parking space on their own in the complex parking lot environment. The technology also can solve the parking problem for some drivers if they have trouble parking, because the vehicle is controlled by the system. The parking lot does not need to prepare much driving space for drivers with poor driving skills, because the driving and parking processes are all controlled by the system, so more parking spaces can be arranged in the same area. In the existing intelligent parking lot guidance systems, vehicles are all controlled by human drivers, so the condition of the parking lot cannot be predicted accurately. It is very hard to plan the route line based on real-time conditions. Road congestion is likely to occur when the traffic volume is large. In our research, we used the Dijkstra algorithm as a basic tool [9; 10; 11; 12]. It is a kind of shortest path algorithm. This algorithm has been used in many areas, such as the pathfinding applications designed by [PERSON], the distribution network optimization problem solved by [PERSON], or the fuel economy area studied by [PERSON] [13; 14; 15]. [PERSON] created a conceptual model of a tourists' guide system [16]. They took the duration of switching traffic lights into account and did further research on time dimension based on the Dijkstra algorithm. In fact, many researchers have made the similar attempt in the parking lot guidance system, such as a route planning scheme for a parking lot designed by [PERSON] et al. or a parking guidance algorithm proposed by [PERSON] [17; 18]. Their researches saved a lot of time for vehicle costs on the road, but the uncertain factors of human drivers will bring many errors into the system. They will not be suitable for the automatic valet parking system. In the automatic valet parking system, the parking lot is implemented in the V2X environment [19; 20; 21]. In the V2X environment, vehicles can exchange information with other vehicles or infrastructures based on vehicle networking. Also, all the vehicles in the parking lot are all controlled by the base station. Real-time road information in the parking lot, such as the vehicle's driving route, parking time, etc., can be transmitted through the communication network to the base station. The information is used for the parking lot control system to perform the calculation of the parking space allocation and route planning of the subsequent vehicles [22]. The combination of the V2X environment and driverless technology is a big breakthrough in valet parking technology. It has been a great help in making sure of the real-time condition and predicting future conditions in the parking lot. Based on the Dijkstra algorithm and combined with the dynamic influence factors of the valet parking lot, this paper designed a route planning scheme to reach each parking space in the shortest time for an automatic valet parking lot. The contributions of this paper are described as follows:  
1. The combination of the V2X environment and driverless technology has been a great help in making sure of the real-time condition and predicting future conditions in the parking lot. This paper designed a method to transform the dynamic influence factors in the parking lot into data based on the new technology for further calculation. 2. Based on the obtainment of the high-precise data in the new technology environment, this paper designed a route planning scheme to reach each parking space with the shortest time. This scheme is suitable for a driverless parking lot.