The National Hockey League introduced the four-referee system – two-referees, two linesmen – for the 1998-99 season. Each team played 20 games under the oversight of a four-man crew. The following year, each team played 50. In 2000-01, the NHL went full-time with the four-man.
NHL Director of Officiating Stephen Walkom takes us through an intro to the system, from communication to positioning and responsibilities.
The AHL introduced the two-referee system in the 2010-11 season, with 25 percent of regular season games and all playoff matches officiated by four-man crews. The league’s goal is to fully transition to the system by 2019. Since 2011, all AHL playoff games have been officiated under the two-referee system.
The ECHL uses one referee in the regular season, but used a two-referee, two-linesman system for all playoff games in 2016.
Internationally, the first major tournament to use the four-man system was the 2008 IIHF World Championships.
The KHL uses a four-man system for all games.