## 4 Results and Discussion
### Traffic Density  
The lane multiplexing strategy is developed to improve the traffic situation of road sections by utilizing the idle road resource in bus lanes. The traffic density is one of the indicators for evaluating the traffic situation of road sections. Figure 7 presents the traffic  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Parameter** & **Value** \\ \hline Signal cycle of the downstream intersection & 100 s \\ Green phase timing of the intersection signal & 25 s \\ Length of the intersection approach & 52.5 m \\ Length of the merging and weaving section & 67.5 m \\ Input car flow & 0-1800 veh/h \\ Bus volume & [30, 60, 90, 120] veh/h \\ Simulation time & 10,000 steps \\ \hline \hline \end{tabular}
\end{table}
Table 3: Experimental simulation parameters.  
density distribution on the experimental link in each case at different bus volume, and it is clear that the traffic density of experimental link increases as input car flow rises.  
When the input car flow is less than 600 veh/h, the traffic density changes almost the same in the three cases, which indicates that the lane multiplexing strategy has almost no impact on the traffic situation of the experimental link in the low-flow traffic environment. In fact, when the experimental link is in a low-flow traffic environment, the cars could achieve the desired velocity in free traffic flow, so there is no need to implement the lane multiplexing strategy to optimize traffic in this situation.  
When the input car flow is greater than 600 veh/h, the traffic density in the three cases shows different trends. The traffic density of Case A is the highest and that of Case C is the lowest, which indicates that the lane multiplexing strategy can improve the traffic situation of the experimental link (i.e., reduce the traffic density of the road section with mixed traffic flow). This should be ascribed to the fact that frequent vehicle lane changes will occur on the mixed road section in the high-flow traffic environment, and this would slow down the traffic and increase the traffic density [42]. The lane multiplexing strategy can effectively control the lane changing of cars by setting the lane-changing area, which can reduce the negative effect of frequent vehicle lane changes on the traffic flow of the experimental link. Analogously, the traffic density that of Case C is lower than that of Case B in the high-flow traffic environment, which indicates that the IBA can further improve the traffic situation of the BLTDM road section by controlling the lane-changing of cars in the downstream intersection area.  
As the bus volume increases, it is found that the traffic density of Case B and Case C tends to increase in high-flow traffic environment, which can be ascribed to the fact that  
Figure 7: Traffic density distribution on the experimental link in each case.  
the lane multiplexing strategy will reduce the resource proportion of cars using bus lanes to ensure bus priority. It can be expected that with the further increase in bus volume, their traffic density will gradually approach the traffic density of Case A. When the bus volume is large enough, the bus lane in the BLTDM road section will become a bus-only lane (i.e., DBL).  
Note that in our simulations, buses flow through the road section evenly and on time, and the bunching issue is not considered. Based on the operation mechanism of the lane multiplexing strategy, the bunching issue actually weakens the influence of the strategy on the traffic flow of the road section [21]. For example, if there is a bunch of three buses passing through the road section, the dynamic bus lane system provides bus priority as if there is only one bus. The time-space for prioritizing each bus has almost overlapped, which is actually an excellent circumstance because cars do not suffer as much as the even bus flow. The situation in our study represents the extreme case for verifying the influence of the lane multiplexing strategy upon traffic flow.