Which condition indicates a risk of collision for an approaching vessel?

Which condition indicates a risk of collision for an approaching vessel?

• A. Generally steady range and increasing bearing
• B. Rapidly increasing range
• C. Constant range with zero bearing change
• D. Only when direct signaling occurs

Answer: (D)

The key idea is how the other vessel appears from your point of view as you close the distance. A real warning of collision is when the other vessel stays on the same line of sight (the bearing doesn’t change) while the distance between you decreases. In other words, constant bearing with decreasing range means you are on a collision course unless one of you alters course or speed. Why this matters: if the bearing shifts as you both move, you’re not on a collision path—the other vessel is passing off to one side. If the range is increasing, you’re separating, so there’s no collision risk. If the range stays the same while the bearing also stays fixed, you’re effectively moving parallel at the same distance, which isn’t a collision threat by itself. Signaling, by itself, doesn’t create a collision risk; it’s the relative motion that matters for safety. So, the best indicator is a constant bearing with decreasing range, signaling that you’re on a potential collision course and action should be taken to avoid it.

The key idea is how the other vessel appears from your point of view as you close the distance. A real warning of collision is when the other vessel stays on the same line of sight (the bearing doesn’t change) while the distance between you decreases. In other words, constant bearing with decreasing range means you are on a collision course unless one of you alters course or speed.

Why this matters: if the bearing shifts as you both move, you’re not on a collision path—the other vessel is passing off to one side. If the range is increasing, you’re separating, so there’s no collision risk. If the range stays the same while the bearing also stays fixed, you’re effectively moving parallel at the same distance, which isn’t a collision threat by itself. Signaling, by itself, doesn’t create a collision risk; it’s the relative motion that matters for safety.

So, the best indicator is a constant bearing with decreasing range, signaling that you’re on a potential collision course and action should be taken to avoid it.