## 3 Methodology
### Pedestrian Feature Modules  
#### 3.3.1 Pedestrian Interference State Feature Module  
As is well known, interactions between pedestrians, e.g., talking and chasing, can affect pedestrians' observations of road conditions and lead to incorrect crossing decisions. Although this problem has received particular attention in pedestrian intention recognition or prediction, in general, existing studies have mainly focused on the interactions between pedestrians by using the distance between them [15], which cannot meet the requirements of all realistic situations, especially when two pedestrians are moving side-by-side in a narrow view-obscured area. Even though they have a small distance between them, an interactive relationship between them cannot be guaranteed. In fact, not only does the distance between pedestrians have an impact on the evaluation of pedestrian interactions but also other factors, such as the azimuth angle between pedestrians, the body pose angle of pedestrians, and the type of pedestrian movement have significant impacts on the determination of pedestrian interactions. There are four aspects to be considered when modeling the pedestrians' interactions, which are described as follows. 1. Distance and azimuth between pedestrians  
The azimuthal angle between pedestrians also affects the judgment of the interactions between pedestrians. For example, when the angle between A and B is 0\({}^{\circ}\), and both of them walk at a slower speed, there is often no interaction between them. Let the mid-hip coordinates of the studied pedestrian be \((x_{8},y_{8},z_{8})\) and the mid-hip coordinates of the other pedestrian be \((x_{8}^{\prime},y_{8}^{\prime},z_{8}^{\prime})\). The distance \(d\overset{i}{t}\) and the angle \(\theta\overset{i}{t}\) between the other pedestrians and the studied pedestrian i at moment t are expressed as follows:  
\[d\overset{i}{t} =\sqrt{\left(x_{8}-x_{8}^{\prime}\right)^{2}+\left(z_{8}-z_{8}^{ \prime}\right)^{2}} \tag{12}\] \[\theta\overset{i}{t} =\arcsin\left(\sqrt{\left(x_{8}-x_{8}^{\prime}\right)^{2}}/d \overset{i}{t}\right) \tag{13}\]  
The orientation relationship between the two is shown in Figure 3.  
Figure 3: Schematic diagram of pedestrian distance and azimuth. On the XOZ plane, Points A and B represent the projections of pedestrians A and B, respectively. Pedestrian head observation angle  
As is well known, humans tend to point their eyes at each other during conversation or other interactions to ensure that the interaction is carried out properly. This is also true for pedestrians. Thus, we take the pedestrian head steering angle \(\alpha\) and shoulder steering angle \(\beta\) into account when performing pedestrian interaction evaluation. Figure 4 shows the definitions of these two angles and the pedestrian torso forward angle \(\gamma\) used later. The head steering angle \(\alpha\)\({}_{t}^{i}\) and shoulder steering angle \(\beta\)\({}_{t}^{i}\) for any pedestrian i at moment t are calculated by  
\[\alpha\)\({}_{t}^{i}=\arcsin\Bigl{(}\sqrt{z_{\alpha\_temp}}/2\Bigl{|}z_{15}^{i}-z_{16}^{i} \Bigr{|}\Bigr{)} \tag{14}\]  
\[\beta\)\({}_{t}^{i}=\arcsin\Bigl{(}\sqrt{\bigl{(}z_{2}^{i}-z_{5}^{i}\bigr{)}^{2}}/ \sqrt{z_{\beta\_temp}}\Bigr{)} \tag{15}\]  
where \(z_{\alpha\_temp}=\bigl{(}z_{15}^{i}-z_{16}^{i}\bigr{)}^{2}+\bigl{(}x_{15}^{i}- x_{16}^{i}\bigr{)}^{2}\), and \(z_{\beta\_temp}=\bigl{(}z_{2}^{i}-z_{5}^{i}\bigr{)}^{2}+\bigl{(}x_{2}^{i}-x_{5 }^{i}\bigr{)}^{2}\). \(x_{15}^{i}\), \(x_{16}^{i}\), \(x_{3}^{i}\), \(x_{6}^{i}\) are the horizontal coordinates of the projection of the right eye, left eye, right shoulder, and left shoulder skeletal points of pedestrian \(i\) in the XOZ plane, respectively; and \(z_{15}^{i}\), \(z_{16}^{i}\), \(z_{3}^{i}\), \(z_{6}^{i}\) are the corresponding vertical coordinates. 1. Action classification During particular interaction behaviors, such as chasing, the pedestrians' heads are not facing the same direction, and the pedestrian spacing may increase over time.