Formula One's governing body has changed its safety car rules to avoid a repeat of the controversy that erupted after last year's title-deciding race in Abu Dhabi.
Race director Michael Masi, who was replaced last month, went against procedure in the closing laps at Yas Marina Circuit to allow Red Bull's Max Verstappen to pass Mercedes' Lewis Hamilton and take the title on the final lap.
With both drivers tied on points going into 2021's final race, the call effectively denied Hamilton a record eighth championship.
Governing body the FIA has now made it clear "all" lapped cars must un-lap themselves before a restart, rather than the more ambiguous "any".
Masi had allowed the race to resume after only the lapped cars between Verstappen and Hamilton, then leading, had unlapped themselves.
It meant not all drivers in the field were treated equally - as lapped cars between Verstappen and third-placed Carlos Sainz's Ferrari, and others further down the field, were left in place. That allowed enough time for one last lap of racing, with the Dutchman on fresh tyres and able to overtake his title rival.
A second contentious rule from the spillover at the Etihad Airways Abu Dhabi Grand Prix will remain in place, the FIA said. This is the requirement the race must be restarted "at the end of the following lap" after the message is relayed that lapped cars may now overtake.
Masi ignored this rule and restarted the race at the end of the lap on which he had ordered only some lapped cars to pass the leaders. Had he followed the rules, the race would not have restarted and Hamilton would have been world champion.
Masi has since been replaced by two officials, Niels Wittich and Eduardo Freitas, who will share the race director job as part of a wider restructuring of the refereeing process.
They will be assisted by FIA stalwart Herbie Blash who will return as permanent senior advisor, having retired in 2016 after 50 years in the sport. Blash was previously assistant to the late race director Charlie Whiting.
The new season starts in Bahrain this weekend.
