Final answer:
An upward hand and arm signal from a driver typically indicates a plan to turn right (or left in countries with left-side driving), and is crucial for communication and safety on the road.
Step-by-step explanation:
When a driver's hand and arm are extended upward, it indicates an intention to turn right in countries where you drive on the right side of the road, or an intention to turn left in countries where you drive on the left side. This hand signal is used as a way to communicate with other drivers when a vehicle's turn signals are not functioning or to make one's intentions clearer in difficult driving conditions. It is imperative for both safety and adherence to traffic laws to understand and correctly use hand signals while driving.