Double hull tankers have traditionally been viewed as offering a higher level of oil spill prevention as compared to single hull construction, because the outer, double hull of the vessel can be penetrated without causing a release of cargo. Several studies have demonstrated that the rate of oil outflow from a double hull tanker involved in a grounding or hull breach is generally less than from other tanker designs. Practical experience supports these studies, as there have been a number of incidents where a double hull tanker’s outer hull has been breached, but pollution has been avoided by the containment afforded by the intact inner hull.