## 3 Proposed Smart Route: IoV-Based Congestion Detection and Avoidance (CDA) Using Rerouting
### IoV-Based Congestion Avoidance (IoV-Based CA)
The influence of different segment sizes on travel time is also shown in Figure 5. Here, it can be seen that proposed scheme performs very well in moderate segment length (i.e., 1000 m), but the performance of MCDP [20] scheme improves as compared to the proposed scheme at 1200 m segment size and onward. The proposed IoV-based CDA scheme selects route by vehicle density without considering the travelling time. However, at long segments (1200 m and onward) under given specification, the chosen path is less dense as compared to the MCDP's [20] selected route. However, due to the speed limit constraint, the travel time of IoV-based CDA is longer than the travel time of the MCDP scheme. Lastly, this section also presents the influence of travelling speed concerning various AOI's segments sizes. It is determined from the result in Figure 6 that the travelling speed gradually increases with the increase of segment size. However, the travel speeds in the IoV-based CDA case remained constant (i.e., 33 m/s) at 1000 m size. It is because of the speed limit of the AOI's segment. Figure 4: Effect of various segment sizes on IoV-based CDA path cost (previous MCDP scheme [20]). Figure 5: Effect of various segment sizes on IoV-based CDA travel time (previous MCDP scheme [20]). ### Impact of Congestion Level on IoV-Based CDA Scheme Performance

In this section, the proposed scheme is assessed under four different congestion levels (i.e., low, medium, high, massive (very high)). Here, the selected performance metrics (i.e., path cost, travel time, and travel speed) are assessed and compared with the MCDP [20] scheme under the aforementioned congestion levels. The path cost is directly proportional to the congestion levels. By increasing the congestion level, the path cost also increases, as shown in Figure 7. It is also depicted that the proposed IoV-based CDA significantly outperforms than the previous MCDP [20] scheme in all congestion levels. The path cost substantially increases in the massively congested scenario in both schemes. In the highly congested scenario, the large number of vehicles increase the occupancy level of the road's segment significantly, which subsequently affects the path cost. The assessment of the second performance metric, i.e., travel time is also shown in Figure 8. In a low congested scenario, most of the vehicles use the direct short-route instead of the alternate best route, that is why the occupancy level of the direct route increases, which further affect the travel time. Since the proposed IoV-based CDA selects an optimum route based on occupancy rate and occupancy time in real time, thus the travel time is significantly lower than the MCDP [20] scheme. Similarly, in all congestion levels, the proposed IoV-based CDA outperforms the MCDP [20] scheme in terms of travel time. However, in the congested scenarios, the difference between both schemes' performance is minor because of the long path cost on all routes. Lastly, this section discusses the assessment of the travelling speed metric over the performance of the IoV-based CDA and MCDP [20] scheme. In Figure 9, the variation of travelling speed in both schemes (IoV-based CDA and MCDP [20]) is shown. The path cost has the same impact on travelling speed like travel time. It can seen that the travelling speed in the low congested scenario is very high in both schemes due to the little path cost. However, in a highly congested scenario, the travelling speed is significantly low because of the high occupancy rate or path cost. Typically, the inter-vehicle spacing reduces in the highly congested scenario because of the high occupancy rate; which further reduces the subsequent time headway. In the case of short-time headway, the driver will reduce the speed significantly to maintain a safe journey. Figure 6: Effect of various segment sizes on IoV-based CDA travelling speed (previous MCDP scheme [20]). Figure 8: Effect of various congestion levels on IoV-based CDA and MCDP travel time.