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Concepts

Collision vs Allision

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.

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