What should drivers do when approaching or upon the crest of a grade and curve of a highway?

When approaching or upon the crest of a grade and curve of a highway, drivers should not attempt to pass to the left. This is due to the limited visibility and the potential for unexpected situations that can arise as the road changes in elevation and direction. The crest of a hill can obscure oncoming traffic or obstacles, making passing a dangerous maneuver.

Maintaining safety is the primary concern in these situations. By refraining from passing, drivers minimize the risk of collisions and ensure they have a clear view of the road ahead when visibility is restored. This is especially important because curves can hide vehicles, pedestrians, or hazards that may suddenly appear.

In contrast, options such as increasing speed or maintaining current speed could lead to a loss of control or an inability to react appropriately to other vehicles or obstacles. Therefore, avoiding passing in these scenarios is crucial for the safety of all road users.