# Median U-Turn Intersection Critical Parameter Research and Operational Performance Evaluation
## 6 Sensitivity Analysis
### Effect of the Separation Distance and the Gap of the Median U-Turn on Average Vehicle Delay  
As two important elements in MUT intersection design, the separation distance and the gap of the median U-turn have a significant effect on the operational performance of MUT intersections. In this subsection, different combinations of separation distance and gap of the median U-turn will be analyzed to examine their effects on delay reduction. The gap of the median U-turn is set to 4 m, 6 m, 8 m, 10 m, and 12 m. The separation distance on the east and west sides of the modified MUT intersection is set to 108 m, 112 m, 116 m, 120 m, 124 m, 128 m, 132 m, 136 m, 140 m, and 144 m, and 72 m, 76 m, 80 m, 84 m, 88 m, 92 m, 96 m, 100 m, 104 m, and 108 m, respectively. The remaining settings for the simulation experiments remain unchanged. Figure 11 illustrates the delay reductions for different combinations of the separation distance on the east and west sides of the modified MUT intersection and the gap of the median U-turn. As shown in Figure 11, when the separation distance on the east and west sides of the modified MUT intersection is certain, increasing the gap of the median U-turn results in only a limited improvement in delay reduction. Only a small portion of the results indicate continued growth in delay reduction. It is considered that appropriately widening the gap of the median U-turn can help reduce average vehicle delay to some extent. However, an excessive gap at the median U-turn allows multiple left-turn vehicles from either the \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Comparison**} & & \multicolumn{2}{c}{**Day 1**} & \multicolumn{2}{c}{**Day 2**} & \multicolumn{2}{c}{**Day 3**} & \multicolumn{2}{c}{**Day 4**} & \multicolumn{2}{c}{**Day 5**} \\ \cline{3-11}  & & **SV** & **CV** & **SV** & **CV** & **SV** & **CV** & **SV** & **CV** & **SV** & **CV** \\ \hline \multirow{3}{*}{Current MUT intersection} & Average vehicle delay & \multirow{3}{*}{51.3} & \multirow{3}{*}{48.5} & \multirow{3}{*}{56.6} & \multirow{3}{*}{52.8} & \multirow{3}{*}{57.2} & \multirow{3}{*}{53.6} & \multirow{3}{*}{52.2} & \multirow{3}{*}{49.5} & \multirow{3}{*}{54.2} & \multirow{3}{*}{51.3} \\  & Error & & & & & & & & & \\ \cline{1-1} \cline{3-11}  & Average vehicle delay & \multirow{3}{*}{46.1} & \multirow{3}{*}{42.9} & \multirow{3}{*}{48.6} & \multirow{3}{*}{45.3} & \multirow{3}{*}{49.4} & \multirow{3}{*}{46.1} & \multirow{3}{*}{45.6} & \multirow{3}{*}{42.9} & \multirow{3}{*}{48.4} & \multirow{3}{*}{46.2} \\  & Error & & & & & & & & & \\ \hline \multirow{3}{*}{Modified MUT intersection} & Average vehicle delay & \multirow{3}{*}{46.1} & \multirow{3}{*}{42.9} & \multirow{3}{*}{48.6} & \multirow{3}{*}{45.3} & \multirow{3}{*}{49.4} & \multirow{3}{*}{46.1} & \multirow{3}{*}{45.6} & \multirow{3}{*}{42.9} & \multirow{3}{*}{48.4} & \multirow{3}{*}{46.2} \\  & Error & & & & & & & & & \\ \hline \hline \end{tabular} SV indicates the simulation result of VISSIM; CV indicates the simulation result of cellular automata. Error = (SV – CV)/SV\(\cdot\)100%.  
\end{table} 
Table 6: The simulation results of the cellular automata model and VISSIM model. major or minor road to turn around simultaneously. This can more severely disrupt the normal driving of the straight-through vehicles on the major road and lead to increased average vehicle delays. Therefore, the benefit of delay reduction will decrease under certain conditions. Overall, it can be said that the effects of the gap of the median U-turn on the operational performance of MUT intersections are quite limited. When we consider the separation distance on the west (or east) side of the modified MUT intersection and the gap of the median U-turn as reference coordinates, it can be observed that increasing the separation distance on the opposite side leads to a corresponding reduction in average vehicle delay. However, as the separation distance on both sides continues to increase, the degree of delay reduction begins to stabilize or even decline.