THE AFL has confirmed it will again experiment with using four field umpires over the bye period in rounds 13-15.

It was first used for selected games late in 2015, after a trial in that year's pre-season.

Umpires coach Hayden Kennedy said the GPS results of whistleblowers would be analysed to see if an extra on-ground official would allow umpires to be less fatigued, and also if they have improved positioning for decision-making.

"In this three-week period, with less matches being played, we can again look at what impact it has across all AFL games without stretching the resources of the current senior list," Kennedy said.

Some umpires will be in charge for a Friday night game and then again on a Sunday.