Patchwork international regulations govern cargo ships like the one that toppled Baltimore bridge

The patchwork system of safety regulations pertaining to massive cargo ships like the one that toppled a major bridge in Baltimore this week can allow freight transporters to skirt oversight, critics say, making maritime shipping what one expert called “the weakest link in the transportation system.”

The thousands of container ships that carry more than 80% of all goods moved around the world are governed by rules established by the International Maritime Organization in that are enforced by the various countries where ships are based and ports across the world. And many ships fly the flags of so-called countries of convenience that offer cheap registration