# Coordinated Multi-Platooning Planning for Resolving Sudden Congestion on Multi-Lane Freeways
## 1 Introduction
Note that, in the literature, the ideas of forming vehicle platoons for traffic coordination are not new [12, 13, 14, 15, 16]. These techniques are useful for increasing the capacity of roads and reducing fuel consumption for long-distance transportation companies. However, maintaining multiple cooperative platoons effectively through a 5G V2V sidelink for resolving temporary bottlenecks of vehicles in emergency situations has not been well explored yet. Unlike the work in [5,10], this work aims to seek a decentralized coordinated planning solution for multiple platoons under high congested traffic contexts where vehicles automatically build a consensus plan for movement and collision avoidance to pass through the bottleneck areas safely. All of the negotiation procedures for the consensus plan are carried out through 5G V2V communications. Specifically, in order to avoid hitting a roadblock created by accidents, lane-changing activities are inevitable. Nevertheless, inappropriate lane changes can threaten instability and cause a collision chain. Hence, controlling incoming traffic and maintaining smooth movements of multiple platoons simultaneously to resolve both traffic congestion and the fairness of exiting is critical. To deal with these challenges, we propose an aggressive platoon management scheme where platoons of vehicles are built based on the vehicle location, velocity, and distance to the accident spot to ensure that vehicles can safely pass through the bottleneck. For example, as illustrated in Figure 1, an accident spot in Lane 0 blocked all approaching vehicles in the same lane. If these vehicles are moving at a high velocity, without good coordination, the vehicles can get stuck in the congestion area or even drift and cause accidents (the shockwave area). As discussed above, we developed a traffic coordination model to build platoons of vehicles to pass the accident spot quickly and avoid potential collision. Generally, as shown in Figure 1, approaching vehicles in Lane 0, Lane 1, Lane 2, and Lane 3 are grouped into platoons in the order of their arrivals and have the same lane priority when passing the accident spot. The vehiclesin different lanes (e.g., Lane 0, Lane 1) can be formed into a platoon and then ordered to change lanes (to Lane 1) and exit the blocked spot. Finally, in the last section, the vehicles of a platoon can go at the maximum velocity to pass the accident spot. To perform the maneuvers mentioned above, in this work, we assumed that every vehicle is equipped with an Advanced Driver Assistance System (ADAS) and V2X onboard units. In short, our contributions are summarized as follows. * We propose an efficient Coordinated Multi-platooning Planning (CPP) scheme where vehicles are grouped into the chain of platoons to pass through temporary bottlenecks safely. * We used CACC/ACC models to support joining platoon and lane-changing procedures and optimized the platoon-forming process in various traffic contexts. * The proposed model can support a macro-coordination scheme in small areas (in V2V communication range) or cooperation in handling the traffic control in large areas (via multi-hop communications). Our source code is available at [[https://tinyurl.com/etraco](https://tinyurl.com/etraco)]([https://tinyurl.com/etraco](https://tinyurl.com/etraco)) accessed on 24 August 2022 for further research. The remainder of this paper is organized as follows. Section 2 describes the related work. Section 3 describes the system model and problem description. Section 4 describes the platoon-based coordination scheme of the dynamic vehicle model. Section 5 describes our implementation and experimental results. Finally, the conclusions and future works are summarized in Section 6. Table 1 summarizes the notations used in this article.