When travelling on a vessel with an enclosed car deck, when should commercial vehicles start engines prior to disembarking?

It is essential that you only start engines when the stern ramp/bow visor has started to open or when a crew member instructs you to do so. Please don’t start your engines prior to this.  

This is important in helping to reduce the levels of elemental carbon (soot) within vehicle decks of those vessels with enclosed car decks - namely MV Isle of Mull, MV Caledonian Isles and MV Isle of Lewis.