MASS Time-to-Collision
Time-to-collision between own ship and target based on relative-position vector. Used inside autonomous collision-avoidance algorithms.
TTC
6.67min
Band
Action required - rule-compliant manoeuvre
Formula, assumptions, and limits
$$TTC = \frac{\text{Range}}{\text{Closing rate}}$$
Simplified linear extrapolation - assumes constant bearings and speeds. COLREGS Rule 8 (action to avoid collision) must begin 'early and substantial' - typically at TTC > 12 min for open water, shorter for restricted waters.
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $Range$ | Current range | nm | radar |
| $Closing rate$ | Rate of approach | kn | ARPA |
| $TTC$ | Time to collision | min | result |
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