How often should a driver place emergency warning devices if parked?

Answer: B — 10 minutes

A driver should place emergency warning devices if parked at intervals of 10 minutes because this timeframe is established to ensure proper visibility and safety. In the event of a breakdown or emergency situation, these devices, such as flares or cones, warn oncoming traffic of the hazard, reducing the risk of accidents. The 10-minute guideline strikes a balance; it allows enough time for the driver to safely secure their vehicle and set up the warning devices without unnecessary delay. Waiting longer than this may increase the risk to both the driver and passing vehicles, while setting them up too frequently may not allow others enough time to process the warning effectively. This timeframe aligns with safety best practices recommended in many trucking and highway safety manuals, emphasizing quick action to alert other drivers.