###### Abstract
found that self-driving vehicles can appropriately reduce greenhouse gas and pollutant emissions on the expressway when their penetration rate is smaller than 30%, but the impact when the penetration rate exceeds 30% was not given [12]. [PERSON] et al. announced that as the ICV penetration rate with connected adaptive cruise control (CACC) continues to increase up to 100%, the fuel consumption can be reduced by 10.74% at the maximum degree on expressways [13]. [PERSON] et al. believed that in merging areas of expressways, ICVs with vehicle-to-vehicle (V2V) functions can significantly reduce travel time and fuel consumption through coordinated control between vehicles on the main roads and the ramps [14]. [PERSON] et al. claimed that, on expressways, ICVs with CACC can form fleets, which can reduce the fuel consumption and emissions of the ICVs in the fleets by 3.7% on average compared to ICVs with non-connected ACC. However, it will increase the average fuel consumption and exhaust emissions of other ICVs integrated into the fleets by 0.54% and 4.1%, respectively [15]. As a result, there have been many related previous studies but they mainly focused on the function of the Internet of Vehicles (IoV). On the contrary, realizing V2V information interaction is faced with various restrictions at present such as laws and regulations, technologies, and differences between different vehicle products. In addition, the estimation results of the impacts of IoV on traffic efficiency, energy conservation and emissions reduction are likely to be different from the current results with technological updates, traffic demands and changes in travel modes in the future. The popularization of ICVs cannot be achieved overnight. Firstly, the development of automation and connection technologies of ICVs requires adequate accumulation, studies, iteration and verification [16]. Secondly, it is necessary to explore effective business modelsfor innovative travel modes based on ICVs. Thirdly, ICVs have to be supported by policies and regulations if they are driven on roads. As a result, traditional human-driven vehicles (HVs) and different levels of ICVs are likely to coexist on roads for a long period of time in the future [8]. At present, high-level ICVs cannot be applied immediately because the specific product forms and technologies, as well as the business models, have not yet been determined. Therefore, the accuracy and guidance value of the assessment of the impacts due to ICVs may not be sufficient. However, the technology of low-level and medium-level ICVs equipped with the advanced driver assistance system (ADAS) is relatively mature and has a relatively higher market penetration rate. As a result, the impact estimation of the low-level and medium-level ICV impacts is expected to be more accurate and valuable in guidance. This paper is expected to fill the gap. ACC and automatic emergency braking (AEB) are the main functions of ADAS to control the longitudinal driving behavior [17]. Based on the distance between the self-vehicle and the preceding vehicle, the motion state, and the artificial operation instructions of the self-vehicle, ACC controls the longitudinal speed of the self-vehicle and the time gap between the self-vehicle and the preceding vehicle to improve the driving experience and safety [18]. AEB can monitor the front driving environment in real time, and automatically brake when a collision risk may occur, so as to avoid or reduce the collision [19]. Both of the two functions change longitudinal driving behavior, consequently affecting the state of the traffic flow. Therefore, it is advisable and reasonable to define the concept of'single-lane automatic driving system' (SLADS) to fully characterize the comprehensive changes in the longitudinal driving behavior due to the two functions. SLADS is a comprehensive driving assistance function for a vehicle used in a single lane, i.e., in the longitudinal direction of the vehicle.