Final answer:
A 'turnout' area should be used when allowing cars behind you to pass, promoting the smooth flow of traffic and enhancing road safety.
Step-by-step explanation:
You should use a special "turnout" area when allowing cars behind you to pass. These areas are designated spots on the road where a slower vehicle can pull off the main travel lane to let faster vehicles pass safely. They are especially common in mountainous or hilly areas with single-lane roads, where it's difficult for vehicles to pass. It's important to use turnouts to maintain the flow of traffic and for safety reasons. When preparing for a U-turn or passing other vehicles, turnouts are not typically used.