This year's Six Nations will adopt the 20-minute red cards that were trialled in the autumn.
For the first time in the competition, a player can replace players sent off for technical offenses after 20 minutes in a campaign designed to punish players and not teams.
However, referees can still award full and permanent red cards for deliberate and dangerous misconduct.
Following his successful debut in the Autumn Nations Series, referees will continue to explain any important decisions within games to spectators via microphone.
To speed up the game, kickers have 60 seconds after a try is scored to make changes, and scrums and lineouts must be formed within 30 seconds.
Global legal action designed to protect scrum-halves at the bottom of the rucks, mauls and scrums will also come into force for the Six Nations.
The Six Nations begin with Wales' trip to France on Friday, January 31. Scotland host Italy and England travel to Ireland the following day.
