# Prototype Network for Few-Shot Hazard Assessment of Vehicle Lane Changes in Risk Field
## 2 Analysis of Lane-Change Behavior and Data Extraction
### Analysis of Lane-Change Behavior
#### 2.1.2 The Variables that Affect Lane-Changing Behavior  
The development of lane-changing behavior is closely related to the traffic environment. Similar to the factors that affect other driving habits, the primary factors that influence lane-changing behavior are the drivers' intention to change lanes and the traffic conditions on the side they intend to move to. Furthermore, the safety implications of nearby vehicles also affect the decision making of lane-changing vehicles during the process [23; 24]. In lane-changing behavior, the ability to effectively judge the volume of traffic in the area is essential. The ability to change lanes freely depends mainly on the subjective will of the driver. When the current lane traffic conditions cannot meet the driver's driving requirements, the lane-changing behavior must satisfy the following requirements. First, the target lane should ensure enough lane-changing space so that the vehicle will not cause any traffic safety problems when entering the lane. This mainly depends on the vehicle making the lane change and the target lane before and after the relationship between the vehicle's speed and distance. Second, there should be enough space for the lane change to proceed smoothly. It depends on the speed and distance of the vehicle ahead in the same lane, as the lane-changing vehicle needs to enter the target lane before colliding with the vehicle in front.  
In order to establish a lane-change model that is more in line with the actual lane-change situation, the mutual position relationship between the lane-change vehicle and the surrounding vehicles needed to be further studied [25; 26]. As shown in Figure 2, the subject vehicle (SV) is the vehicle for which the lane-change occurs. Vehicle \(n-1\) (preceding vehicle, PV) is the vehicle in front of the same lane, and vehicle \(n+1\) (following vehicle, FV) is the rear vehicle in the same lane. Vehicle \(n-2\) (lead vehicle, LDV) is the vehicle ahead of the target lane, and vehicle \(n+2\) (lag vehicle, LGV) is the vehicle behind the target lane. Vehicles SV, PV, LDV, and LGV are separated by \(g_{E-1},g_{T-2}\), and \(g_{T+2}\), correspondingly [27].  
Vehicle SV may want to change lanes. If any of the following situations occur while the vehicle is in motion, it may change lanes. Here are three common reasons for a lane change.  
* The subject vehicle, SV, is faster than vehicle PV in front of the current lane. There is enough space in front of the target lane for a lane change (\(g_{T-2}\)),meeting the lane change requirement. The distance between the main vehicle, LGV, and the vehicle behind the target lane (\(g_{T+2}\)) is greater than the minimum safe following distance.  
Figure 1: Diagram of the trajectory of vehicle switching to the right (**a**). Diagram of the trajectory of a vehicle’s lateral displacement (**b**). The three horizontal lines represent schematic lane markings, while the blue line indicates the trajectory of a vehicle changing lanes to the right.  
* Vehicle LDV in front of the target lane is faster than vehicle SV in the current lane. The distance (\(g_{T+2}\)) between vehicle LGV and the vehicle behind the target lane is greater than the minimum safe following distance.
* The FV behind the current lane is mostly to blame for safety problems between the SV and the FV behind it, such as tailgating. Studies on lane-shifting behavior do not consider the relationship between speed and distance from vehicle FV.  
Based on the above analysis, vehicle SV must consider the headway relationship with the vehicle in front of the same lane, the vehicle in front of the target lane, and the vehicle behind the target lane [28].