TCPA (Time to Closest Point of Approach)
Abbreviation: TCPA
The time remaining until own ship + a target reach their Closest Point of Approach — the primary time-window indicator for collision-avoidance action.
Regulatory detail & full definition
Time to Closest Point of Approach is the time to CPA if both vessels maintain course + speed. Combined with CPA, TCPA tells the OOW when the collision-risk window is — a target with CPA 0.3 NM + TCPA 20 min needs early action; CPA 0.3 NM + TCPA 3 min is imminent. ARPA + ECDIS displays; alarms typically set at TCPA 12 min in open water.
Authoritative source: IMO — Radar + ARPA ↗
Related
Source: IMO ARPA performance standard
High confidence
Editorial confidence: how we grade.