Abstract-Intelligent vehicle cooperation based on reliable communication systems contributes not only to reducing traffic accidents, but also to improving traffic flow. Adaptive Cruise Control (ACC) systems can gain enhanced performance by adding vehicle-vehicle wireless communication to provide additional information to augment range sensor data, leading to Cooperative ACC (CACC). This paper presents the design, development, implementation and testing of a CACC system. It consists of two controllers, one to manage the approaching maneuver to the leading vehicle and the other to regulate car-following once the vehicle joins the platoon. The system has been implemented on four production Infiniti M56s vehicles, and this paper details the results of experiments to validate the performance of the controller and its improvements with respect to the commercially available ACC system.

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Currently, Adaptive Cruise Control (ACC) systems can automate vehicle speed control to maintain following time-gaps in the range of one to two seconds. In this study, a field test was conducted to determine whether or not drivers would be comfortable with the sub-second following time-gaps that could be provided by a Cooperative ACC (CACC) system. A CACC system uses vehicle-vehicle communication to enable faster system responses and shorter following time-gaps. Sixteen drivers from the general public drove both systems on their daily commuting trips, and their driving behavior and subjective opinions of the systems were recorded. The results show that the drivers were generally comfortable with and typically selected the sub-second following time-gaps offered by the CACC system, but there were significant differences between the preferences of male and female drivers. The male drivers typically preferred the shortest gap settings, while the female drivers typically preferred slightly longer gap settings. The drivers' willingness to accept the shorter following gaps adds credibility to the assertion that future CACC systems may have the potential to produce significant increases in the achievable highway lane capacity.

Cooperative adaptive cruise control (CACC) includes multiple concepts of communication-enabled vehicle following and speed control. Definitions and classifications are presented to help clarify the distinctions between types of automated vehicle-following control that are often conflated with each other. A distinction is made between vehicle-to-vehicle (V2V) CACC, based on vehicle–vehicle cooperation, and infrastructure-to-vehicle CACC, in which the infrastructure provides information or guidance to the CACC system (such as the target set speed value). In V2V CACC, communication provides enhanced information so that vehicles can follow their predecessors with higher accuracy, faster response, and shorter gaps; the result would be enhanced traffic flow stability and possibly improved safety. A further distinction is made between CACC, which uses constant-time-gap vehicle following (forming CACC strings), and automated platooning, which uses tightly coupled, constant-clearance, vehicle-following strategies. Although adaptive cruise control (ACC) and CACC are examples of Level 1 automation as defined by both SAE and NHTSA, the vehicle-following performance that can be achieved under each scenario is representative of the performance that should be expected at higher levels of automation. Implementation of CACC in practice will also require consideration of more than the lowest level of vehicle-following and speed regulation performance. Because CACC requires interactions between adjacent equipped vehicles, strategies are needed such as ad hoc, local, or global coordination to cluster CACC vehicles. Some of the challenges that must be overcome to implement the clustering strategies are discussed as well as strategies for separating CACC clusters as they approach their destinations, as potential traffic improvements from CACC will be negated if the vehicles cannot disperse effectively.