# Study on the Extraction Method for Ecological Corridors under the Cumulative Effect of Road Traffic
## 2 Method
### Resistance Surface Construction
#### 2.2.2 Road Traffic Resistance Estimation  
Road traffic hinders the communication of reptiles on both sides due to the constant passage of vehicles, on the one hand, and causing animals to be reluctant to approach due to noise and dust on the other hand. With the increase in road network density, the impact of noise and dust will accumulate and intensify, and the impact map is shown in the following figure.  
As shown in Figure 2, \(a\) and \(b\) are two roads, and the thick boxes \(A\) (dashed line) and \(B\) (solid line) correspond to the impact areas of \(a\) and \(b\), respectively. The figure contains the following elements:, (1) spatial distribution of road \(a\), \(b\); (2) impact region of road \(a\); (3) impact region of road \(b\); (4) superimposed impact region of roads \(a\) and \(b\), divided into three regions (\(O\), \(P\), \(Q\)) from top to bottom, impact region (\(O\)) of road \(a\), common impact region of roads \(a\) and \(b\) (the middle short vertical line covering the region \(P\)), and impact region (\(Q\)) of road \(b\). The influence degree of region \(P\) is the cumulative amount of \(a\) and \(b\) influence values, and this calculation method is applicable to the spatial propagation of noise, dust, lighting, and other influence factors. For a single road, the closer to the road, the greater the impact, and then as the distance between roads gradually increases, the impact gradually decreases until it disappears. As an extreme example, if road \(a\) can only be passed during the day, road \(b\) can only be passed at night, and the sound of vehicles moving can only be heard in region \(O\) during the day and in region \(Q\) at night, while noise can be heard in region \(P\) throughout the day. This superimposed effect must be noted.  
Figure 2: Road traffic impact diagram.  
\(F\) is the impact value of the road, \(f\) is the impact value as a function of distance, and _dis_ is the linear distance between the target point and the road.  
\[F=f(dis) \tag{5}\]  
From Formula (5), roads \(a\) and \(b\)'s respective impact functions can be obtained, as shown in Formulas (6) and (7).  
\[F_{a}=f(dis_{a}) \tag{6}\]  
where \(F_{a}\) is the influence value of road \(a\) and \(dis_{a}\) is the linear distance between the target point and road \(a\).  
\[F_{b}=f(dis_{b}) \tag{7}\]  
where \(F_{b}\) is the influence value of road \(b\) and \(dis_{b}\) is the linear distance between the target point and road \(b\).  
In the range where both road \(a\) and \(b\) can be influenced (such as the above \(P\) region), their joint influence can be expressed as \(F_{ab}\).  
\[F_{ab}=f(dis_{a})+f(dis_{b}) \tag{8}\]  
Figure 3 shows a map of the spatial distribution of road traffic resistance in a part of Wuhan. The maximum impact distance of road traffic is set at 1000 m, and it can be seen that the denser the roads, the greater the resistance value. More typical is the vicinity of the road intersection, whose resistance value is significantly higher than other surrounding areas. In addition, the more bifurcations there are, the higher the resistance value will be.