Early Warning Method and Model of Inland Ship Collision Risk Based on Coordinated Collision-Avoidance Actions

Table 1

Process of early warning method of inland ship collision risk based on coordinated collision-avoidance actions.

Distance to the closest point of approach (DCPA)	Time to the closest point of approach (TCPA)	Coordination degree for collision-avoidance actions of two ships (Co)	Early warning conclusion
DCPA > MinDCPA	TCPA > MinTCPA	Any value	When R is small, there is no collision risk
DCPA ≤ MinDCPA	TCPA > MinTCPA	Co∈[1, Co1]	A collision risk exists, but it is not yet imminent; an alert is issued that the two ships have not yet understood each other’s movements
		Co∈[Co1, Co2]	A collision risk exists, but it is not yet imminent; the vessels have understood each other’s movements; an alert is issued that the vessels have not unified their collision-avoidance strategies
		Co∈[Co2, Co3]	A collision risk exists, but it is not yet imminent; the vessels have understood each other’s movements and unified their collision-avoidance strategies; an alert is issued that the vessels have not yet taken coordinated maneuvering actions
	0 < TCPA ≤ MinTCPA	Co∈[Co3, e]	The collision risk is imminent; the vessels have understood each other’s movements, unified their collision-avoidance strategies, and taken coordinated maneuvering actions; an alert is issued that the vessels have to verify the effectiveness of their collision-avoidance actions