# Efficient Traffic Flow Guidance Feedback Strategy Considering Drivers' Disobedience in ITS
## 4 Simulation Results and Discussion
### Simulation Scenario and Performance Evaluation  
In our simulation scenario, a route called the \"original route\" was first considered. We have chosen to make most of the arriving vehicles pass through the original route. The spare routes are also needed if the drivers are asked to change their route to avoid congestion.  
In SUMO, if the entrance is congested by vehicles, newly arriving cars will not enter the scenario; therefore, in order to avoid such a situation caused by the congestion on other routes, the possibility of congestion on the other route must be limited at the lowest level. In the simulation, a three-route scenario was designed. The system will ask drivers to change to either spare route randomly. The three-route scenario is shown in Figure 1.  
The route in the middle is the original route, and the other two routes are the spare routes. A total of 80% of the vehicles entering the scenario are assumed to pass through the original route, while 10% of the vehicles are assumed to pass through each spare route. At the end of the scenario, the three routes share an intersection, and a traffic light is designed to create congestion on the original route.  
The length of the original route is 680 m. The lengths of the spare routes are both 704.86 m. The traffic light is green for 30 s on the original route and for 40 s on both spare routes.  
One vehicle will enter the scenario per second. The acceleration of each vehicle is 1.2 m/s\({}^{2}\). The deceleration of each vehicle is 4.5 m/s\({}^{2}\). The maximum speed for each vehicle on each route is 50 m/s (180 km/h). To ensure the diversity of driver behaviors when following other vehicles, a driver imperfection parameter is added with values taken in [0, 1], where 0 denotes a perfect driver. The simulation starts at time step = 0 and ends at time step = 1799. The duration of the simulation is thus 1800 s in total.  
In real life, it is impracticable for systems to collect road data and give instructions every second because of the limit on processor speed and data transfer speed; the surveillance period was set to 30 time steps (30 s) in the simulation. This means that the system collects the route/vehicle data and decides whether to give instructions or not every 30 s.  
During each surveillance, the locations of vehicles on the route as well as their velocities are recorded, and the dynamic weighted vehicle density is calculated. A congestion threshold is used, just as mentioned in Section 3.4. If the dynamic weighted vehicle density surpasses the threshold, it is considered congestion, and the system will have to give instructions to the newly arriving drivers; otherwise, the system will not give instructions to drivers. In the simulation, several values of the threshold are tested, and in the end, the threshold value is set to 0.1. If the threshold is set too high, congestion will be detected too late.  
If the system decides to instruct the newly arriving driver to change to a new route, it will choose one of the two spare routes randomly with equal probability \(w\). This option will help to reduce the probability of congestion on the two spare routes.  
The performance evaluation was carried every 5 time steps (5 s). During each evaluation, the mean vehicle speed and the number of vehicles that are not moving, were recorded. The flux is calculated, as in [21], with the following formula:  
\[F=V_{mean}\times N/L \tag{4}\]  
where \(V_{mean}\) denotes the mean velocity of all vehicles on the route, \(N\) stands for the number of vehicles on the route, and \(L\) is the length of the route. The flux indicates the mean number of vehicles that pass through the route per second.  
Figure 1: A three-route scenario.  
Finally, a timer was added to record the duration of each congestion during the simulation. After the simulation, the mean congestion duration was also calculated.