When is it appropriate to switch drivers during a long trip?

Switching drivers during a long trip should be done when it is safe and necessary to do so, which makes this the most appropriate answer. Safety is crucial, and knowing when to rotate drivers helps ensure that every driver is alert and capable of handling the vehicle effectively. Factors such as fatigue, the need for breaks, or even shifting road conditions can influence the decision to switch drivers.

Choosing to switch when it feels safe acknowledges that driver's ability to operate the vehicle will vary based on multiple personal and environmental factors. This can enhance overall safety for everyone in the vehicle and others on the road. Flexibility in this decision can contribute significantly to road safety and the overall effectiveness of long-distance travel.

The other options may suggest somewhat rigid approaches to driver rotation that don't necessarily account for the real-time conditions of fatigue or attention levels that can fluctuate throughout a trip. Focusing solely on feeling tired or only switching at predetermined stops might not always align with the best timing for a switch, as the need can arise unexpectedly based on how each driver is feeling.