The EF81 is a series of Bo-Bo-Bo locomotives for use under 1.5 kV DC and 20 kV AC. The prototype was completed in 1968 and a total of 160 further locomotives was completed by Hitachi and Mitsubishi by 1992. These were split among several batches which had a similar outside appearance and could only be distinguished by details like the headlights. Some had been built for traffic through the Kanmon undersea tunnel and had bodies of unpainted corrugated stainless steel. All had six 425 kW traction motors and delivered 2,550 kW under AC, but only 2,370 kW under DC. By 2016, the number of EF81 in service had fallen to 44.