## 3 Proposed Smart Route: IoV-Based Congestion Detection and Avoidance (CDA) Using Rerouting
### IoV-Based Congestion Avoidance (IoV-Based CA)
The detail of all parameters is given in Table 1. Two different simulation experiments are performed to evaluate the performance of the proposed IoV-based CDA scheme, as given below:

1. **Experiment A:** The first experiment is about the impact of various segment sizes (i.e., from 300 m to 1500 m) over the performance of IoV-based CDA. The number of vehicles for each road segment is kept constant for all segmental sizes. 2. **Experiment B:** The performance of IoV-based CDA is assessed under various traffic conditions. Four different traffic conditions are considered in ONE-kilometer long road's segment, i.e., low traffic congestion (5-20 vehicles), medium traffic congestion (20-40 vehicles), high traffic congestion (40-60 vehicles), and massive (very high) traffic congestion (60-100 vehicles). To assess the performance of the proposed IoV-based CDA over the experiments, as mentioned earlier, we used three prominent performance metrics for evaluation, i.e., path cost/occupancy level, travel time, and travelling speed. The definition of each metrics is given below:

1. **Definition of Path cost/Occupancy level:** It is the ratio of the current number of vehicles to the total capacity of the road's segment. This metric represents the level of congestion of a given segment. The higher the value of path cost, the greater will be the congestion level. This metric can also be used to measure throughput. Throughput refers to the number of vehicles reached successfully to their destination. 2. **Definition of Travel time:** This metric represents the time during which the source vehicle reaches the destination. The mathematical definition of travel time is \[T(t)=\frac{L_{seg}*N_{seg}}{V_{limit}}\] (6) The travel time \(T\) depends on segment length \(L_{seg}\), number of segments \(N_{seg}\) as well as the speed limit \(V_{limit}\). The appropriate speed on each segment is also depended on the congestion level. 3. **Definition of Travelling speed:** It is the speed in which the vehicles can travel without collision. In safety travelling, speed can be calculated as below: \[Space\_Gateway=\frac{L_{seg}*N_{seg}}{No.of\text{re}ticles}\] (7) \[Travelling\_speed=\frac{Space\_Gateway}{\tau}\] (8) Where \(Space\_Gateway\) and \(\tau\) represent the inter-vehicle spacing and safety time to cover the inter-distance, respectively. The performance metrics, as mentioned earlier, are calculated under different specifications. ### Impact of AOI's Size on IoV-Based CDA Scheme Performance

The capacity or occupancy of AOI's increases with the increase of an individual segment's size (Based on Equation (7)). In this section, the impact of AOI's segment's size on IoV-based CDA performance is evaluated in terms of path cost, travel time, and travelling speed. It is shown in Figure 4 that the increase of segment size has a positive effect on path cost. The path cost significantly reduces in IoV-based CDA as well as in the MCDP [20] scheme with the increase of AOA's size. However, the performance of the proposed scheme is better than the previous MCDP [20] scheme due to the real-time route planning. \begin{table}
\begin{tabular}{l l} \hline \hline
**Parameter** & **Value** \\ \hline No. of segments & 13 \\ No. of junctions & 9 \\ Length of vehicle & 5 m \\ Minimum safety gap & 10 m \\ Time headway \(\tau\) & 2s \\ Occupancy rate threshold \(\delta\) & 0.7 \\ Occupancy time \(\mathcal{O}_{t}\) & 0.6 s \\ Segment length & [300 m, 600 m, 900 m, 1200 m, 1500 m] \\ Congestion levels & Low, Medium, High, Massive (very high) \\ Low congestion & 5–20 vehicles \\ Medium congestion & 20–40 vehicles \\ High congestion & 40–60 vehicles \\ Massive congestion & 60–100 vehicles \\ Simulation time & 500 s \\ RSU coverage & 1000 m \\ MAC protocol & IEEE 802.11p \\ Propagation model & Two ray-ground \\ Scenarios types & 2 (varying segment size, temporal simulation) \\ Performance metrics & Path cost, Travel time, Travelling time \\ No. of lanes & 2 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation parameters.