Module 5 - COLREGs
COLREG Rule 7: assessing risk of collision
Use all available means appropriate to the circumstances to determine whether risk of collision exists. If there is any doubt, treat the risk as existing. Build a sequence of observations: visual bearings and range trend, radar plotting or equivalent systematic observation when radar is fitted and operational, plus sight, hearing and the developing geometry. AIS can add useful identity and movement information but does not replace this assessment.
A bearing that does not appreciably change while range decreases is a strong warning of collision risk. An appreciable bearing change does not automatically prove safety, however, especially with a very large vessel, a tow or another vessel at close range. Avoid conclusions from a single observation or scant radar information; confirm the trend early enough to take substantial and readily apparent action under Rule 8.
- If in doubt, risk of collision EXISTS
- Constant bearing + decreasing range = collision risk
- Use a series of observations, not one bearing or one electronic snapshot
- Use radar properly, including long-range scanning and systematic observation, when fitted and operational
- An appreciable bearing change may still conceal risk at close range or with a large vessel or tow
Watch for this: Take a series of timed bearings and ranges. If the bearing remains broadly steady while range closes, treat it as collision risk and decide early; never use AIS CPA alone as the verdict.
Sources and factual review
Reviewed 12 August 2026 - Compass Revision editorial review.
Apply Rule 7 to complete encounters
The COLREGs module links lookout, safe speed, risk assessment, avoiding action and vessel responsibilities.