# A Systematic Literature Review of Autonomous and Connected Vehicles in Traffic Management
## 3 Research Analysis
### Traffic Management Methodologies Consisiting of Primary Goals
#### 3.2.3 Safety and Efficiency  
Enhancing the usefulness of suggested approaches in practical contexts requires finding the optimal balance between several aims. As a result, the articles in this section took both efficiency and safety into account. One study [43] suggested an ideal scheduling technique imagining the arrival time of AVs at the junction to reduce delays and increase safety. They used MILP to tackle the organizing issue, decreasing the frequency of stops and delays at crossings while preventing accidents. The suggested solution reduces average driving time and average halted wait by 7.6% and 52.5%, correspondingly, as contrasted with conventional traffic signal arrangements. Additionally, ref. [95] proposed a practical and safe technique called the customized synchronous intersection protocol (CSIP), a powerful and extensive variation of the ballroom intersection protocol (BRIP). CSIP employs a predefined inter-vehicle distance to get over this restriction and reduces the number of stops at the junction, since BRIP poses a danger of crashes due to positioning errors. As per the simulation findings, customized synchronous intersection protocol outperforms ballroom intersection protocol related to the number of trip delays and accidents. One study [26] addressed the issue of managing junction crossing traffic effectively and safely for connected and autonomous ground vehicles. They created a method known as a trajectory-based intersection traffic coordination algorithm for discrete-time occupations to achieve this goal (DICA). In the event of a communication breakdown, ref. [96] outlined a unique distributed intersection algorithm to prevent collisions and reduce delays at the junction. They discovered that the suggested approach successfully addresses numerous unidentified communication problems. Autonomous reservation-based intersection control (AReBIC), a novel approach [97], was proposed to reduce dispute and overall delay and to enhance mobility during an emergency evacuation. The recommended solution outperforms the current traffic control strategy in terms of average speed, overall delay, and conflicts and combines movement priority with a reservation methodology. To make intersections safer and reduce wait times, ref. [27] recommended a preassigned-slots approach employing the suitable optimization method for the initial allocation alternately transforming (COMPACT) and location improvement on sequence evaluation (LOOSE) for safety and higher effectiveness to enhance the performance of the target intersection. The suggested approach may shorten the average crossing time, and vehicles can pass through the junction without halting or colliding. For safe and quick intersection crossing, ref. [63] designed a smart multi-agent traffic controller. The suggested approach uses deep neural networks and reinforcement learning (RL) to learn and predict the optimum course of action for each vehicle. Additionally, considering V2I communication, ref. [44] introduced an intelligent in-vehicle decision-support system. It employed a probabilistic sequential decision-making procedure to assist AVs in making better stop/go decisions and minimizing needless stops. Another study [28] created a decentralized coordination method based on sequential optimal control and model-based decision heuristics to tackle the traffic coordination problem. The suggested approach is collision-free and appropriate for quick online implementation. Additionally, ref. [64] described using 5G technologies to create communication-based apps for connected automobiles to increase efficiency and safety when using them. Similarly, ref. [98] described leveraging a 6G network for reliable and effective autonomous vehicle routing. Reference [99] suggested a delay-lenient protocol that considers transmission and network delay to increase junction management systems' safety. The proposed approach surpasses conventional traffic signals in performance and average travel time conditions and prevents accidents.