  Safety-critical distributed cyber-physical systems (CPSs) have been found in
a wide range of applications. Notably, they have displayed a great deal of
utility in intelligent transportation, where autonomous vehicles communicate
and cooperate with each other via a high-speed communication network. Such
systems require an ability to identify maneuvers in real-time that cause
dangerous circumstances and ensure the implementation always meets
safety-critical requirements. In this paper, we propose a real-time
decentralized reachability approach for safety verification of a distributed
multi-agent CPS with the underlying assumption that all agents are
time-synchronized with a low degree of error. In the proposed approach, each
agent periodically computes its local reachable set and exchanges this
reachable set with the other agents with the goal of verifying the system
safety. Our method, implemented in Java, takes advantages of the timing
information and the reachable set information that are available in the
exchanged messages to reason about the safety of the whole system in a
decentralized manner. Any particular agent can also perform local safety
verification tasks based on their local clocks by analyzing the messages it
receives. We applied the proposed method to verify, in real-time, the safety
properties of a group of quadcopters performing a distributed search mission.
