# Research on a Collaborative Control Strategy of an Urban Expressway Merging Bottleneck Area
## 4 An Illustrative Example
### Effect Evaluation
#### 4.3.2 Traffic Efficiency Improvement Analysis
Considering that the speed data in a short time interval fluctuates greatly, 5 min is used as the data interval to count the speed difference data of each segment. The distribution of speed difference (time speed difference) between adjacent time intervals of each segment of the experimental road under the uncontrolled state. Under the uncontrolled state, the speed difference is between \(-\)15.1 km/h and 7.6 km/h, the range is 22.7 km/h, the standard deviation is 3.5911, and the speed difference is generally distributed between \(-\)8 km/h and 8 km/h, as shown in Table 11. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Sum** & **Max** & **Min** & **Median** & **Standard Deviation** & **Range** \\ \hline Uncontrolled & 27,643 & 2.46 & 44.28 & 24.67 & 7.95 & 41.82 \\ Cooperative control & 29,319 & 2.48 & 43.92 & 24.81 & 7.16 & 41.44 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Turnover results. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Segment** & **Min** & **Median** & **Max** & **Range** & **Standard Deviation** \\ \hline Cell1 & \(-\)6.79 & \(-\)1.38 & 6.16 & 12.95 & 3.6959 \\ Cell2 & \(-\)7.79 & \(-\)1.3 & 6.92 & 14.71 & 3.6555 \\ Cell3 & \(-\)8.24 & \(-\)1.15 & 6.9 & 15.14 & 3.4471 \\ Cell4 & \(-\)9.12 & 0.89 & 4.22 & 13.34 & 3.5556 \\ Cell5 & \(-\)14.4 & \(-\)0.95 & 5.9 & 20.3 & 4.5390 \\ Cell6 & \(-\)15.1 & \(-\)0.9 & 7.6 & 22.7 & 4.3206 \\ Cell7 & \(-\)7.92 & \(-\)0.9 & 5.1 & 13.02 & 3.1406 \\ Cell8 & \(-\)7.8 & \(-\)0.73 & 5.7 & 13.5 & 3.2511 \\ Cell9 & \(-\)8.7 & \(-\)1.15 & 4.92 & 13.62 & 3.0098 \\ Total & \(-\)15.1 & \(-\)0.97 & 7.6 & 22.7 & 3.5911 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Uncontrolled time speed difference. Figure 19: Comparison of Travel Time and Turnover Change before and after Simulation Segment Control. (**a**) Travel time comparison; (**b**) Turnover comparison. As shown in Figure 20, the distribution of speed difference (time speed difference) between adjacent time intervals of each segment of the experimental road is shown when the two merging areas are opened for cooperative control. It can be seen from the diagram that after the application of cooperative control, the speed difference and fluctuation range of adjacent time intervals of each segment are reduced. Due to the application of variable speed limit control, the speed change of Cell2 and Cell5 segments is larger than that of other segments, but at the same time, the speed drop range of Cell3 and Cell6 segments located downstream is controlled, especially the speed drop range of the merging bottleneck segment at Cell6 is significantly improved. As shown in Table 12, the statistical results of the speed difference data show that the speed difference is between \(-6.9\) km/h (a decrease of \(54.30\%\)) and \(4.98\) km/h (a decrease of \(34.47\%\)), the range is \(11.88\) km/h (a decrease of \(47.67\%\)), and the standard deviation is \(2.6614\)(a decrease of \(25.89\%\)). The speed difference is generally distributed between \(-5\) km/h and \(5\) km/h. Compared with the uncontrolled state, the range and standard deviation of the speed difference between adjacent time intervals of each segment are reduced, and the distribution range of the speed difference is more intensive, indicating that the traffic flow of each segment is more uniform in time distribution, and the sudden change of traffic flow speed is reduced. Figure 20: Time speed difference under coordinated control. As shown in Figure 22, the spatial speed difference distribution of each adjacent segment is shown when the two merging areas are opened for coordinated control.