A warning signal must be given before the maneuver:
Immediately before starting the maneuver.
Simultaneously with the beginning of the maneuver.
In advance, before the start of the maneuver.✓Bonne réponse
Explication
The warning must precede a maneuver by enough time to communicate the driver's intention before the vehicle changes direction or position. A signal given at the instant movement starts cannot serve as advance notice, although it should also not be given so early that it misleads others.