## 5 Sensitivity Analysis
### Sensitivity Analysis Results
There is no notable distinction between Scheme 3 and Scheme 1 for all diverging ratios within the traffic volume range of 1320 to 3300 veh/h, only a small improvement in CO emissions. The improvement ratio of Scheme 3 exhibits its greatest significance when the traffic volume surpasses 3300 veh/h. Figure 5: Improvement ratio of Scheme 2 compared to Scheme 1. (**a**) Delay, (**b**) travel time, (**c**) CO emission, and (**d**) number of conflicts. Figure 6d shows that at the diverging ratio of 10-40% and traffic volumes of 1320-3960 veh/h, Scheme 1 has a much lower number of conflicts and higher safety. However, when the traffic volume exceeds 3960 veh/h, Scheme 3 has a greater improvement ratio in the number of conflicts, reaching a maximum of 100%. When the diverging ratio is 50%, the improvement is positive for all traffic volumes. This situation occurs due to the escalating traffic volumes and diverging ratio; the demand for diverging and emerging increases, resulting in complex traffic conditions upstream of the diverging area. For Scheme 1, vehicles in the auxiliary lanes have no insertion gap to emerge into the mainline. As a result, they need to slow down or even stop, leading to waiting near the diverging area. This situation contributes to an increase in the number of conflicts. However, Scheme 2 extends the auxiliary lane to a certain distance behind the diverging nose to ensure that vehicles have enough distance to emerge into the mainline. From the above analysis, it can be seen that Scheme 3 outperforms Scheme 1 in terms of efficiency, environmental protection, and safety. This difference becomes particularly pronounced when the diverging ratio exceeds 30% and the traffic volume exceeds 3960 veh/h. In these scenarios, the improvement is most obvious. * Comparison of Scheme 4 and Scheme 1  
Figure 7a shows that Scheme 4 has a higher delay than Scheme 1 when the diverging ratio of 10% and traffic volume range from 1320 to 1680 veh/h. However, for the rest of the traffic combinations, there is a significant improvement, typically within the range of 30% to 75%. The maximum improvement, reaching 84.69%, is achieved at 30%, 4620 veh/h. Figure 7b shows that Scheme 4 demonstrates either no improvement or minimal improvement in terms of travel time when the traffic volume remains below 4620 veh/h. The improvement ratio is greater when the traffic volume is greater than 4620 veh/h. The maximum improvement ratio reaches 71.67% at 40%, 6600 veh/h. Figure 7c shows that Scheme 4 improves CO emissions under all traffic conditions, and the improvement becomes larger as the diverging ratio increases but gradually decreases when the diverging ratio exceeds 40%. The maximum improvement ratio occurs at 40%, 6600 veh/h. Figure 6: Improvement ratio of Scheme 3 compared to Scheme 1. (**a**) Delay, (**b**) travel time, (**c**) CO emission, and (**d**) number of conflicts. In terms of the number of conflicts, Scheme 4 presents a disadvantage, with no improvement in the diverging ratio of 10%. For the rest of the diverging ratio cases, when the traffic volume is only 5280-6600 veh/h, there is a large improvement ratio in Scheme 4. In summary, since Scheme 4 is the B-type weaving area, some vehicles directly emerge into the mainline without changing lanes, so the traffic efficiency is high. However, it is important to note that Scheme 4 has certain inherent drawbacks. Specifically, the absence of auxiliary lanes for transitioning on the emerging ramp, which directly emerges into the mainline, poses a significant risk for accidents. Therefore, it verifies the situation in Figure 7d; the safety is poorer compared to Scheme 1.