The criteria for determining which ports should become compulsory are:

		Degree of difficulty and hazard in the approaches and within the port itself.
		Amount of vessel movement and maneuverability and the size of those vessels.
		Nature of cargo carried on board (e.g. oil, gas, explosives, hazardous materials).
		Design of wharves, slips and actual space available for maneuvering.
		Environmental concerns and the preservation of the ecosystem.