When the danger of collision between vessels occurs, the proper interpretation of radar information will indicate that, with respect to the manœuvring rules, any avoiding action should always be positive. However, it is well known that radar information is not always properly interpreted. Misinterpretation may cause a situation to be assessed as ambiguous. This, in turn, may produce disagreement, on both vessels, about how the rules should be correctly applied. To solve this difficulty, some authors propose communication between the vessels. Others think the avoiding action of any vessel should automatically be such that the sight line rotates in the anti-clockwise direction. (The latter suggestion results in a port-to-port passing whilst the vessels cross with a port bearing from the aspect of the overtaking ship.) Complications may arise from either proposal.