ABSTRACT: The North Atlantic right whale Eubalaena glacialis is endangered, in part, due to vessel-strike mortality. We use vessel traffic and right whale survey data (~3 nautical miles [n miles], ~5.6 km resolution) for the Bay of Fundy and on the Scotian Shelf (northwest Atlantic) to determine the relative risk of lethal vessel encounters by using 2 estimates: (1) the event—the relative probability of a vessel encountering a right whale, and (2) the consequence—the probability of a lethal injury arising from an encounter. For the Bay of Fundy region our estimates demonstrate that the relative risk of lethal collision could be reduced by 62% by means of an amendment to the traffic separation scheme (TSS) that intersects a Right Whale Conservation Area. In the Roseway Basin region of the Scotian Shelf, the majority of vessels navigate outside of a Right Whale Conservation Area, although the highest relative risk is concentrated within the Conservation Area where fewer vessels navigate at greater speed. Here, our estimates demonstrate that a seasonal recommendatory area to be avoided (ATBA) could be designed to reduce the risk imposed by vessels upon right whales in the region. Our estimates contributed to the International Maritime Organisation (IMO) adoption of a TSS amendment in the Bay of Fundy and an ATBA on the Scotian Shelf. Thus, the goal of achieving the greatest reduction in the risk of lethal vessel-encounters with whales, balanced by some minimal disruption to vessel operations while maintaining safe navigation, can be achieved.