Mental calculation while assessing collision avoidance situation. Quick calculation is a good tool in deciding which and when do you take action. There a lot of diskartes and this is one of them. When will this target be clear? When can I get one mile clearance? Do I have enough sea room after 12 minutes? Target A will be ahead of me while target B will be behind me in xxx minutes therefore in xxx minutes I can safely alter to port/starboard. This thought process can greatly enhance your navigat