## 3 Analysis of Traffic Characteristics
### Flow Speed  
The traffic flow speeds with and without the implementation of a contraflow strategy were compared to better examine the effect of the contraflow strategy on the traffic characteristics. Statistical analysis showed that, for the same traffic volume, the flow speed under regular conditions was significantly lower than that under the contraflow strategy. This can be explained by the fact that the added contraflow lane bore a substantial amount of the traffic pressure and directly improved the outbound road capacity. As indicated in Table 1, for a given traffic volume of 2500 veh/L, the normal lanes under regular conditions were almost saturated, whereas they still performed well when the contraflow strategy was employed. With increasing traffic volume, the speed difference between the two conditions gradually decreased as the lanes approached their maximum capacities. The comparison of the average speeds of 38.06 and 37.44 km/h of the normal lanes under regular conditions for traffic volumes of 2500 and 3500 veh/h, respectively, with the average speed of 39.20 km/h under contraflow conditions demonstrates this point. In addition, the flow speed of the contraflow lane was lower than that of the normal lanes under contraflow conditions, specifically by 8-13 km/h. Through independent sample \(t\)-tests of vehicle speed under different traffic volumes under contraflow conditions, a significant difference was found to exist between the vehicle speeds on the normal and contraflow lanes (\(p<0.05\)). Furthermore, the speed variations of the different lanes under regular and contraflow conditions were analyzed to investigate traffic safety. It is generally accepted that the occurrence of road accidents such as front-to-rear collisions and sideswiping are related to traffic speed variation, with a larger speed variation increasing the probability of such accidents. In Table 1, the speed variation of the contraflow lane is always higher, which may be attributed to driver unfamiliarity and anxiety due to the reversal of the typical driving direction. In addition, the speed variation was observed to generally decrease with increasing traffic volume. The speed variation on each lane is also associated with road safety. It is usually easier for drivers to be distracted and decide to change lanes when the traffic on their current lane is moving much slower than that on another lane. Overall, a larger traffic volume decreases the driving speed on a lane but increases the safety level. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Traffic** & \multicolumn{3}{c}{**Regular**} & \multicolumn{3}{c}{**Contraflow Condition**} \\
**Volume** & **Speed (km/h)** & **Condition** & & & & \\
**(veh/h)** & & **Normal Lane** & **Entry** & **Exit** & **Normal Lane** & **Contraflow Lane** \\ \hline
2000 & Average speed & 50.00 & 34.14 & 34.73 & 67.52 & 54.23 \\  & Speed variation & 8.84 & 5.16 & 4.33 & 10.43 & 18.22 \\
2500 & Average speed & 38.06 & 29.43 & 27.56 & 58.86 & 49.01 \\  & Speed variation & 5.97 & 5.62 & 4.35 & 8.49 & 16.36 \\
3500 & Average speed & 37.44 & 27.31 & 25.02 & 39.20 & 30.57 \\  & Speed variation & 5.50 & 4.18 & 3.49 & 5.29 & 12.07 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Average speed and speed variation (km/h) on different lanes under regular and contraflow conditions. Figure 3 shows the traffic density data collected from the normal and contraflow lanes with and without the implementation of the contraflow strategy. The chart reveals a slight difference between the traffic densities of the normal lanes with and without contraflow. With increasing traffic flow, the density of the normal lanes was a little higher than that of the contraflow lane, which can be attributed to the haste of the drivers to get to their destinations. However, the difference between the flow densities of the normal and contraflow lanes was significant. The traffic flow of the normal lanes reached its maximum when the density was approximately 30 veh/km/L, while that of the contraflow lane was 40 veh/km/L.