How do I flag an incident in my sector?

MSA Appendix H (2026):

• Waved yellow at your post: danger in the sector after your post. Signal drivers by hand or flag to use the clear part of the track.
• Double waved yellow (two flags at one post): a very serious obstruction, or a total blockage before the Clerk of the Course stops the race.
• Preceding post: while you wave yellow, the post before you shows a stationary yellow (two stationary yellows if you are showing double waved) to give drivers early warning.
• If debris spreads into the next sector, that post also shows yellow. Otherwise the next clear post shows green to mark the end of the yellow zone.
• Drivers passing any yellow must slow down, be ready to stop, hold position and not overtake until past the green flag.
• Red flag: waved at every post on the Clerk of the Course's instruction to stop the session, except the post just before the incident, which shows double waved yellows.

Flags must be at least 60 cm by 80 cm. All posts must be in radio or telephone contact with the preceding post so the no-passing procedure works.