In some cases, the ships designed and classified as ice-strengthened ships have certain level of icebreaking capabilities. For example, the SA-15, a typical Russian freighter capable of operating in the Arctic which is described in detail later, was constructed with ice-strengthened grade according to the Russian classification and is capable of continuous icebreaking of ice up to 1m thick. Vessels that have some slight icebreaking capability, even when classified as ice-strengthened, are sometimes defined as icebreaking ships. It should be noted that terms such as "ice-going", "ice-transiting", "ice-worthy" and "icebreaking" frequently appear with different definitions in the literatures.
In terms of regulations governing ice-strengthened ships, a broad similarity is recognized among the rules of the various classification societies. For example, NK's regulations on ice-strengthened ships are essentially based on FSICR regulations. FSICR classifies ice-strengthened ships from the very strict IA super class to the more general ID class but theoretically accepts corresponding classes established under other regulations. This is in contrast with the case of icebreakers. A few classification societies, such as NK and FSICR, carry no specific rules for icebreakers. In fact, none of the standards of administrations and classification societies are readily comparable, or even compatible with one another. They are not consistent, as they are mostly based on different concepts of the forces experienced at the ship and ice interface.
As the foregoing discussion shows, while a certain amount of harmonization exists among the classification societies' regulations regarding ice-strengthened ships, essentially each classification society sets its own rules. This problem has been recognized and the relevant organizations are working toward one set of harmonized international standards for the construction and navigation of ships in polar seas, in particular in the northern ice-covered waters. (Karaminas, 1999). The opening of the NSR forms a substantial background to these initiatives.
