Final answer:
A driver extending his hand and arm downward is signaling an intention to stop or slow down; it is crucial for road safety, especially when brake lights are not functional.
Step-by-step explanation:
When a driver's hand and arm are extended downward, he is signaling that he intends to stop or slow down. This hand signal is important for communicating with other drivers, especially when a vehicle's brake lights are not working. A driver extending his hand and arm downward is signaling an intention to stop or slow down; it is crucial for road safety, especially when brake lights are not functional.
In light of traffic safety, these signals are an essential part of driver education and road-sharing etiquette. For instance, in a scenario where many vehicles speed through the intersection without regard to the posted speed limit, understanding and correctly interpreting hand signals can prevent accidents and ensure safer road conditions.