What does the driver’s manual NOT suggest doing when you pass a vehicle?

Whenever you are about to pass a vehicle, pedestrian, or bicyclist, assume they do not see you. They could suddenly move in front of you. When it is legal, tap the horn lightly or, at night, flash your lights from low to high beam and back. Drive carefully enough to avoid an accident, even if they do not see or hear you. [California Commercial Driver Handbook]