This activity shall consider the transitions of the AS from autonomous to non‐autonomous operation when it crosses the ODM boundary. This seeks to identify ways in which those transitions could be unsafe such that suitable mitigations can be provided. This requires as input an ODM transition model ([JJ]) for the AS. Based on the transition model, the ways in which the possible AS transitions may be unsafe shall be determined. This will allow measures to be defined to minimise the risk of the unsafe transitions for the AS operation. The table in Figure 27 in the ODM transition model ([JJ]) provides examples of the nature of typical unsafe transitions. The transitions in the table refer to those from the ODM transition model ([JJ]) shown in Figure 28 in ([JJ]).
An autonomous ship can self‐navigate without intervention as long as it has sufficient channel width margins. If it progresses down a seaway of varying width, the autonomous navigation function may need to engage and disengage, repeatedly handing control to the ship’s crew. In this scenario there are a number of different unsafe transitions that could occur. This includes remaining in autonomous control when the channel width becomes too narrow (which may be beyond the safe capability of the autonomy), as well as relinquishing control when in a wide channel (when the crew may not be in a position to safely take control). In certain situations the ship may attempt to mitigate such deviations by getting back inside the defined ODM, for example by taking a route that involves wider channels.
The results of assessment of the transitions shall be documented along with any assumptions made ([LL]).