  A cooperative intelligent transport system (C-ITS) uses vehicle-to-everything
(V2X) technology to make self-driving vehicles safer and more efficient.
Current C-ITS applications have mainly focused on real-time information
sharing, such as for cooperative perception. In addition to better real-time
perception, self-driving vehicles need to achieve higher safety and efficiency
by coordinating action plans. This study designs a maneuver coordination (MC)
protocol that uses seven messages to cover various scenarios and an abstracted
MC support service. We implement our proposal as AutoMCM by extending two
open-source software tools: Autoware for autonomous driving and OpenC2X for
C-ITS. The results show that our system effectively reduces the communication
bandwidth by limiting message exchange in an event-driven manner. Furthermore,
it shows that the vehicles run 15% faster when the vehicle speed is 30 km/h and
28% faster when the vehicle speed is 50 km/h using our scheme. Our system shows
robustness against packet loss in experiments when the message timeout
parameters are appropriately set.
