Because JNR DD13 diesel locomotives were not powerful enough for heavy work like hump work in a freight yard, JNR DD20 diesel locomotives were produced experimentally, and ended in failure.
貨物ヤードでのハンプ作業のような重作業に対応出来る機関車は国鉄DD13形ディーゼル機関車では力不足であり、国鉄DD20形ディーゼル機関車が試作されたものの失敗に終わった。