F1 drivers have been warned over track limits at the Radillion corner at Spa-Francorchamps, with lap times set to be deleted if drivers go to the left of the kerb.
The rule will also apply during the three practice sessions that precede Saturday's qualifying session, while drivers will also be monitored during the race.
Race director Michael Masi wrote in his race notes: "A lap time achieved during any practice session or the race by leaving the track and cutting behind the apex of Turn 4, as judged by the detection loop in this location, will be invalidated by the stewards.
"On the third occasion of a driver cutting behind the apex of Turn 4 during the race, he will be shown a black and white flag, any further cutting will then be reported to the stewards.
"Each time any car cuts behind the apex, teams will be informed via the official messaging system."
Masi added that there was an exception, as the rule will "not automatically apply to any driver who is judged to have been forced off the track" and that "each such case will be judged individually".
In a revised version of the notes, a previously written rule written to punish drivers who crossed the red/white/green chevron separating the pit entry and the track was crossed out.
It is also stated that the use of tyre blankets in the pit lane during the race is prohibited on the grounds of safety.