What happens when the starter aborts a start but nobody false-started?

Under World Athletics Rule TR16.5, the starter aborts the start when, after "On your marks" or "Set", an athlete:

1. causes the start to be aborted without a valid reason, for example by raising a hand or standing or sitting up from a crouch start
2. doesn't comply with the commands, or doesn't take their final position at once and without delay
3. disturbs other athletes by sound, movement or otherwise

Consequences:

• For (1) or (2), the referee may warn the athlete for improper conduct, and disqualify them for a second infringement in the same competition. No green card is shown.
• For (3), if it caused another athlete to commit what would otherwise be a false start, the referee may warn (disqualify on a second infringement); otherwise a green card is shown. Repeated movements at several aborted starts can still earn a warning.
• If an outside cause led to the abort, or the referee disagrees with the starter, a green card is shown to all athletes to show no false start was committed.

The starter or a recaller also recalls the race whenever the start was not fair, including blocks slipping or something interfering (TR16.10). For hearing-impaired athletes, a flag, strobe or other visual signal may be used alongside the gun (TR16 S1).