  This paper presents a distributed solution for the problem of collaborative
collision avoidance for autonomous inland waterway ships. A two-layer collision
avoidance framework that considers inland waterway traffic regulations is
proposed to increase navigational safety for autonomous ships. Our approach
allows for modifying traffic rules without changing the collision avoidance
algorithm, and is based on a novel formulation of model predictive control
(MPC) for collision avoidance of ships. This MPC formulation is designed for
inland waterway traffic and can handle complex scenarios. The alternating
direction method of multipliers is used as a scheme for exchanging and
negotiating intentions among ships. Simulation results show that the proposed
algorithm can comply with traffic rules. Furthermore, the proposed algorithm
can safely deviate from traffic rules when necessary to increase efficiency in
complex scenarios.
