If you have a Radar it will probably be set to use ARPA to assist you in deciding whether you are on a collision course with another vessel . Many yachts have now added AIS to their nav electronics and can overlay the AIS targets on to the Radar and chart plotter display to add more information. So far the logic is that you calculate the Closest Point of approach (CPA) and Time to Closest Point of approach (TCPA) and make a judgement on which way to turn according to the Collision Regs.
SafePass is an idea from Fred Pot of SeaCAS. In this scheme the system calculates various CPA/TCPA results and plots “safe” and “dangerous” zones on your current heading to make it even easier to decide which new heading may be appropriate for your vessel. This depends on the other vessel not changing course and also on the circumstances of the impending collision with regard to the Collision Regs of course.
By the way one of the simplest, most practical and down to earth descriptions of how to use your radar can be found on Bill Dixon & Pat Watt’s personal web page