The 2013 rulebook had five major changes and passing is the final link in these changes. This last one refers to passing which had a few errors in judgement or result over the 2012 season in my opinion. The Tyler McQuarrie and Joon Maeng debacle at Road Atlanta comes to mind as a poor use of the old passing rules. Below you can see the improvement in the rulebook and a quote from Andy Yen.
Updated verbiage on passing.
Formula DRIFT has adjusted the passing verbiage in the rulebook to make it more broad and open. The purpose of this will be to give drivers a chance to attack a lead driver who is making noticeable mistakes and also for the public to be more deeply engaged in the competition.
Passing is allowed in Formula DRIFT. Passing is allowed anywhere on course as long as the lead car is clearly off the line the judges have specified. Any passing that occurs outside the scope of the aforementioned criteria will be deemed illegal and constitute an equivalence to a zero (0) run.
“We made these changes to make judging specific criteria less ambiguous and more defined, which will keep us accountable for consistency,” said Andy Yen, judge for Formula DRIFT. “The new changes will help define the judging without sacrificing the essence of drifting, subjectivity.”