The coupler was originally designed in 1856 by Eli Janney and has been much-improved by the technical branch of the American Association of Railroads (AAR). In the last 10 years, Congress has mandated that couplers on all tank and dangerous non-perishable cars must have protective flanges over and under the knuckle to keep couplers from climbing out of contact during derailments—puncturing connected cars and potentially releasing flammable or hazardous contents.