# Service-Oriented Cooperation Policies for Intelligent Ground Vehicles Approaching Intersections
## 5 Verification Experiments and Analysis
### Experiments and Analysis
This demonstrates that these policies possess the capability to warrant QoS of vehicles with higher priorities. Furthermore, we can find that queue-based policies, covering FAFP-SQ-SV, FAFP-MQ, HWFP-SQ-SV, and HWFP-MQ, have also reduced the delay of vehicles with higher priorities significantly. Especially, HWFP-SQ-SV exhibited the best effect, which is because that the \"-SV\" property allows vehicles on other lanes to obtain unauthorized S-CSs. * Proportion of Large Vehicles: \(P_{v.l=4.5m}\)  
From the models of intelligent vehicles and S-CS, we know that various vehicles with different sizes will occupy different amount of S-CSs when passing through an intersection, and the passing-through time will be also discrepant. Particularly, when taking a left-turning maneuver, larger vehicles will maybe occupy all four S-CSs as shown in Figure 2a, while small vehicles will only enter into three of these S-CSs. Obviously, the latter cases will possibly allow the concurrency of multiple passing-through procedures. So, the influence of the proportion of lager vehicles also needs to be evaluated. Figures 17 and 18 presents a group of experimental results. It is clear that the average delay time of vehicles (H) with queue-based policies still keep lower than that with FAFP-SV and HQEP-SV policies. It can be also concluded that all QoS-oriented policies are effective to guarantee the QoS of vehicles (H) under situations with different \(P_{v.l}\). * Proportion of Vehicles (H): \(P_{H}\) Through experimental results as shown in Figures 19 and 20, it can be found that under normal traffic situations where \(\lambda\) is smaller, all QoS-oriented policies perform better than FAFP-based policies. But these experiments have also proved that, along with the increase of \(P_{H}\) and \(\lambda\), the performance of QoS-oriented policies become more different. Figures 19 and 20 also presents the cooperation effects when \(\lambda\) is 0.8, namely under heavy traffic-jam situations. From this figure, it can be found that all queue-based QoS-oriented policies are still capable to perform well even though the average delay time is increased somewhat. Of course, the exception is that HQEP-SV begins to degrade significantly since \(P_{H}\) exceeds 0.7. This is mainly because when the \(P_{H}\) and \(\lambda\) are all big enough, GPI will promote more vehicles(M,L) to the highest priority that will eliminate the differences of vehicular emergencies. Extremely, HQEP-SV will finally degrade to FAFP-SV. Platoon Length: \(N\)  
Platoon length is in fact the amount of vehicles to be authorized each time. From the common sense, longer one platoon is, shorter the average delay time will be caused. But, it can be also imagined that a bigger platoon will maybe block vehicles on other lanes for a longer time. To find the influence of platoon length, presented as the variable \(N\) within the value scope \([1,10]\), we conduct a series of experiments. Figures 21 and 22 presents the effects under normal traffic situations. From these results, it can be observed that when \(N\) is greater than 1, namely authorizing a vehicular platoon at each time, the average delay time of each queue-based policy decreases obviously, meanwhile, QoS-oriented policies still warrant QoS of vehicles (H) well. Since a flexible value of \(N\) has been employed in queue-based QoS-oriented policies, as described in Algorithms 3 and 4, any vehicle (H) could be authorized in time so long as it has submitted a reservation message. It is also very clear that, when \(N\) is bigger than 4, the average delay time caused by each QoS-oriented policy will level off. Of course, this effect is also relative to some other factors, such as \(d_{r}\), \(P_{H}\), \(P_{vJ}\), and \(\lambda\). (3) Analysis of Throughput at One Intersection  
Keeping high throughput is another important goal for the optimizing of traffic management. During our work, the throughput has been taken into account as well as the main target to authorize vehicles (H) preferentially.