In the Union's match against DC United on Fireworks Night, MLS will be testing its Video Assistant Referee offline as the league tests in the system in all 22 stadiums.
What is VAR?
VAR is an additional official positioned in a booth with technology that allows the referee to access video from every available broadcast camera angle.
What will VAR review?
VAR can only review "game-changing" situations, such as goals, penalty calls, direct red-card incidents and cases of mistaken identity. A communication system will allow the VAR to alert and advise the head referee of when an error is made to then correct the call.