Final answer:
The meaning of a driver's hand and arm being held upward is slow or stop.
Step-by-step explanation:
The meaning of a driver's hand and arm being held upward is slow or stop. This hand signal is used to indicate that the driver intends to slow down or come to a complete stop. It is commonly used when approaching a stop sign, traffic light, or in situations where the driver needs to slow down for pedestrians or other hazards on the road.