In addition to the above payment, the Convention provides for the payment of special compensation to assisters who “carry out assistance operations with regard to a vessel which, by nature or whose cargo, pose a threat to the environment”.

Note: assistance operations concerning mobile drilling units and platforms in addition to State vessels are not covered by the LONDON Convention of 28 April 1989.

General average is a rule specific to maritime law aimed at equitably sharing between the vessel’s owners and cargo owners, the sacrifices (damage or costs) resulting from reasonable measures voluntarily taken by the captain for the necessary common safety of the voyage.

Except in very rare cases, average adjustments are drawn up in accordance with the York and Antwerp rules, conventional rules and common international practices, to which almost all transport and freight contracts refer.

Note: these Rules reserve the right to appeal if the Average is the consequence of a negligence committed by one of the parties involved (for example the vessel’s unseaworthiness before the beginning of the voyage, incompetent crew, etc.)

This is the share that each of the parties involved in the vessel and the cargo must pay for the common sacrifices, in proportion to the residual value of its property (vessel or merchandise) at the end of the voyage. Since this is the equitable sharing of all the sacrifices, the ratio between the contribution and the value of property involved is the same for everyone.

The contribution is due by everyone, whether insured or not. Those who are insured will be reimbursed by their insurer for the contribution paid, whilst others must pay for the amount themselves.

•   Provisional contribution

The drawing up of an average adjustment is generally quite long and can take several years. When the vessel arrives, it is impossible to immediately, exactly or fully calculate the losses and costs accepted as a general average by the average adjuster. The ship-owner assesses them approximately, calculates their percentage of the total value, which is also estimated, with regard to its amount and the conditions in which the merchandise is delivered with the prior payment of a “provisional contribution” calculated based on this data.

Today, in the vast majority of cases, ship-owners accept, instead of paying a provisional contribution, a promise by insurers for the merchandise to duly pay the "final" contribution resulting from the average adjustment. This promise is made in writing by an ‘‘average adjustment guarantee letter’’ issued by the insurer for the ship-owner or the average adjuster.

•    Definitive contribution

It is only when the average adjustment is closed that the "final" contribution will be known for payment by the ship-owner and the owners of the merchandise. If the final contribution is greater than the provisional contribution, an additional payment is due by the participants. On the contrary, if the final contribution is less than the provisional contribution, the excess payment will be reimbursed.