When is it permissible to turn on a curve or crest of a grade?

Turning on a curve or crest of a grade presents visibility and safety challenges due to potential obstructions and the limited line of sight. The correct answer highlights that it is permissible to make such a turn only if the vehicle is visible to approaching vehicles within 500 feet. This visibility is crucial because it ensures that any oncoming traffic has enough time to react and adjust their speed or direction accordingly, reducing the risk of accidents.

The requirement of visibility over a specific distance is grounded in safe driving practices, as being able to see and be seen is a fundamental aspect of road safety. If a driver is unable to see oncoming traffic, it could lead to dangerous situations, particularly on curves or inclines where vehicles may be at risk of colliding due to inadequate reaction time.

Other options might suggest conditions that do not adequately address safety. For instance, an intersection being marked may not guarantee safe visibility or adequate reaction time for both drivers. Simply adhering to speed limits does not ensure that the maneuver can be executed safely, especially if visibility is compromised. Additionally, the absence of nearby vehicles does not rule out unseen traffic, making the requirement of visibility even more critical.