## 4 Results and Discussion
### The Impact of SLADS on Traffic Efficiency and CO\({}_{2}\) Emissions
#### 4.2.2 The Impact of SLADS on Road Capacity under Different Driving Styles  
The influences of SLADS on the road capacity of the expressway and the secondary motorway under different aggressive style ratios of ICVs are shown in Figures 6 and 7, respectively. In view of the fact that the impact of SLADS on the road capacity mainly appears above the saturated service level, as shown in a-c of the two figures, only three different volume inputs were studied, which were the saturated service level, and the 20% and 40% oversaturated service levels. For the expressway, when the volume input is at the saturated service level, the capacity can be maintained near the designed service level as long as the ICV aggressive rate is more than 40%, while a decreasing interval exists in the road capacity if the ICV penetration rate is lower than 40%. In particular, if there is no aggressive ICV on the road, the road capacity will drop significantly as the ICV penetration rate increases. When the volume input reaches the 20% and 40% oversaturated service level, the road capacity is significantly improved as the aggressive style proportion of ICVs increase, and the benefit could be increasingly more apparent as ICV penetration rate increases. Compared with the actual Chinese driving style distribution, when the volume input is at the 20% and 40% oversaturated service level, the road capacity can be promoted by 919.20 pcu/h and1982.40 pcu/h, respectively, as the aggressive ratio of ICVs increases, which is 15.06% and 31.49%, respectively.  
Figure 6: The impacts of SLADS on road capacity of the expressway under different driving styles with the volume input being equal to the saturated service level **(a)**, 20% oversaturated service level **(b)** and 40% oversaturated service level **(c)**.  
For the secondary motorway, when the volume input was not lower than the saturated service level, the higher the aggressive style proportion of ICVs was (not less than 20%), the more obvious the improvement of road capacity was under the same ICV penetration rate. When the aggressive style proportion of ICVs exceeded 20%, a similar improvement trend of the road capacity was observed with the ICV penetration rate becoming larger. Compared with the actual Chinese driving style distribution, when the volume input reached the saturated service level, and the 20% and 40% oversaturated service level, the road capacity could be promoted by 669.00 pcu/h, 1204.80 pcu/h and 1486.80 pcu/h, respectively as the aggressive ratio of ICVs increased, which were 32.35%, 57.93% and 71.21%, respectively. Additionally, as shown in Figure 7a, at the saturated service level, when both the aggressive style ratio and the penetration rate of ICVs reached 100%, the road capacity was close to the actual volume input. This is a reasonable explanation for the phenomenon mentioned in Section 4.1.2 that the actual volume cannot be raised to the volume input under the saturated service level of the secondary road even though the ICV penetration rate has reached 100%. However, as the volume input continues to increase, such a phenomenon will still exist, as depicted in Figure 7b,c.