The Navigation Rules state that any vessel, whether power-driven or under sail, must take all reasonable measures to avoid a collision. This includes giving way to vessels that are on a collision course, as well as those that are constrained by their draft, anchoring or other circumstances. The rules also stipulate that the burden of avoiding a collision lies with the vessel that is underway, unless it is overtaken by another vessel. In general, larger vessels must give way to smaller ones, and those sailing under power must give way to those under sail. There are many other specific scenarios detailed in the rules, but these are the general principles.