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| Early stage | Early warning conclusion | Later stage | Early warning conclusion | Early warning effectiveness |
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Group A | DCPA ≤ MinDCPA and TCPA > MinTCPA | A collision risk exists, but is not imminent | DCPA ≤ MinDCPA and 0 < TCPA ≤ MinTCPA | Imminent risk of collision exists | Ultimately, seven groups encountered close-quarters situations, and one was almost in immediate danger. |
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Group B | DCPA ≤ MinDCPA TCPA > MinTCPA, Co∈[1, Co1] | A collision risk exists, but is not imminent; an alert is issued that the two ships have not yet understood each other’s movements | | | Through step-by-step early warning alerts, when TCPA > MinTCPA, the vessels have understood each other’s movements and unified their avoidance strategies. Ultimately one group was almost in a close-quarters situation, but none encountered immediate danger |
DCPA ≤ MinDCPA TCPA > MinTCPA, Co∈[Co1, Co2) | A collision risk exists, but is not imminent; the vessels have understood each other’s movements; an alert is issued that the vessels have not unified their collision-avoidance strategies | | |
DCPA ≤ MinDCPA TCPA > MinTCPA, Co∈[Co2, Co3) | A collision risk exists, but it is not imminent; the vessels have unified their collision-avoidance strategies; an alert is issued that the vessels have not yet taken coordinated maneuvering actions | | |
| | DCPA ≤ MinDCPA 0 < TCPA ≤ MinTCPA, Co∈[Co3, e] | The collision risk is imminent; the vessels have taken coordinated maneuvering actions; an alert is issued that the vessels have to verify the effectiveness of collision-avoidance actions |
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