Japan is a country of high population density with a large number of railway passengers in relatively small urban areas, and frequent operation of short-distance trains has been required. Therefore, the high acceleration ability and quick turnaround times of MUs have advantages, encouraging their development in this country. Additionally, the mountainous terrain gives the MUs an advantage on grades steeper than those found in most countries, particularly on small private lines many of which run from coastal cities to small towns in the mountains.