## 3 Analysis of Traffic Characteristics
### Flow Speed
The reason for this may be the same as a previous observation, that the drivers on the contraflow lane were affected by those driving in the opposite direction, who were separated from them by only traffic cones, and in addition the unfamiliarity of driving in the reverse direction. Since the overall capacity of the road sections without contraflow (the red segments in Figure 1) were lower than that of the sections with contraflow, bottlenecks were created along the entire road. As also mentioned above, the \"fixed bottlenecks\" at the entries and exits of the contraflow lanes affected the capacity and speed of these lanes. The main reason for this was that the entries and exits of the contraflow lanes were usually across the highway median and were narrow, especially so for large vehicles. Most of the drivers entering a contraflow lane had to decelerate to a low speed and carefully navigate from the normal lane to the contraflow lane. This, as well as the merging flows with traffic in the normal lanes at the exits from the contraflow lanes, was a source of bottlenecks. Before arriving at the entry of a contraflow lane, a driver had to decide whether to enter the contraflow lane. This amounted to an internal interference and altered the driving behavior of the drivers. Furthermore, at the exit of a contraflow lane, a driver had to observe vehicles in the normal lane and look for an opening to merge, with the delay creating a local congestion, the magnitude of which increases with an increasing length of delay. The fundamental solutions to reducing the fixed bottlenecks caused by the contraflow strategy are the adoption of moveable medians on the highway and completely removing them to make the contraflow lane more accessible, and in addition forbidding large vehicles from using the contraflow lane. In addition, traffic cones or other demarcation instruments can be used to separate vehicles in the left-most normal lane from those in the other normal lanes 150-200 m before the entry of the contraflow lane. Vehicles in the left-most lane could decide whether to turn left into the contraflow lane at an entry or continue straight along their normal lane, while vehicles on the other normal lanes can only  
Figure 3: Flow densities with and without the implementation of the contraflow strategy. continue on those lanes. This reduces diverging points and the associated bottlenecks from the other normal lanes, apart from the left-most one. A similar demarcation can be used on the normal lane about 150-200 m before the exit from a contraflow lane. This would keep the left-most normal lane empty at the exit and eliminate merging conflicts. The part of the study discussed in this section considered the overall traffic capacity and speed to establish the characteristics of the entire flow of vehicles. However, it is noteworthy that the contraflow traffic on a four-lane dual highway is actually a single lane, which prevents overtaking. Considering that coaches typically move at a lower speed than those of passenger cars, they often cause the development of a long platoon of vehicles in their trail on a contraflow lane. This constitutes a \"moving bottleneck.\" The effect of this type of bottleneck was also examined in the present study, with the purpose of developing measures for enhancing the efficiency of the contraflow strategy for mass evacuation.