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Concepts

Collision vs Allision

| Term | Definition | |---|---| | **Collision** | Both vessels were **moving** at the time of impact | | **Allision** | One vessel was **moving**; the other was stationary (moored, anchored, or a fixed structure) |

Definitions

TermDefinition
CollisionBoth vessels were moving at the time of impact
AllisionOne vessel was moving; the other was stationary (moored, anchored, or a fixed structure)

Fixed structures count as allision targets

  • Bridge (e.g. Francis Scott Key Bridge)
  • Crane
  • Berth / quay wall
  • Anchored vessel

Why the distinction matters

The causal chain and liability differ significantly. In a collision, both vessels may have contributing factors. In an allision, the moving vessel's navigation, pilotage, or propulsion failure is typically the primary focus.

Browse hubs

  • Collision for vessel-to-vessel cases grouped by primary vessel type
  • Allision for strikes involving fixed, moored, or anchored targets grouped by primary vessel type

Compound types

Both can combine with other types:

  • Collision / Fire — collision leading to fire
  • Allision / Sinking — allision causing flooding and sinking