The meaning of allision in shipping is the situation when a moving vessel strikes a stationary object, such as a dock, a bridge, or another vessel that is not in motion. Allision is different from collision, which involves two moving vessels hitting each other. The distinction between allision and collision is important for determining fault and liability in case of an accident.

According to the Oregon Rule, which is based on a Supreme Court case from 1874, there is a presumption that the moving vessel is at fault for the allision, unless it can prove otherwise. The moving vessel has to show that it was operating with reasonable care, that the stationary object was somehow to blame for the accident, or that the accident was unavoidable due to some external cause. The Oregon Rule applies to both commercial and recreational vessels.

However, if the stationary object was violating a statutory rule of navigation intended to prevent collisions or allisions, then the Pennsylvania Rule applies. This rule states that there is a presumption of causation when a vessel violates a statutory rule of navigation, and the violating vessel has to show that its violation could not have been one of the causes or even a contributory cause of the accident. The Pennsylvania Rule was also established by the Supreme Court in 1874, in the same case as the Oregon Rule.

Allision can cause serious damage to both the moving vessel and the stationary object, as well as injuries or deaths to the people on board or nearby. Allision can also result in environmental harm, such as oil spills or pollution. Therefore, it is important for vessel operators to follow the rules of navigation and exercise caution when approaching or passing near stationary objects. If an allision occurs, the parties involved should report it to the authorities and seek legal advice from a maritime lawyer.