No passing to the left shall be done when:

• A. Approaching or upon the crest of a grade
• B. Curve of a highway
• C. In a no-passing zone
• D. At an intersection

Answer: (A)

Passing to the left requires enough clear sight distance to judge the speed and distance of oncoming traffic. When you’re approaching or at the crest of a grade, your view is blocked by the hill itself, so you can’t tell if an oncoming vehicle is close or coming fast. Attempting to pass in that moment could place you in a head-on collision, which is why this situation is prohibited.

The other scenarios also reduce safety, but for different reasons. Curves limit what you can see around the bend, no-passing zones are specifically marked to forbid passing, and at intersections cross traffic and turning vehicles create complex, unpredictable conflicts. The crest of a grade is the classic case where visibility is abruptly cut off, making passing unsafe.