Under which condition is overtaking on the left NOT acceptable?

Overtaking on the left is not acceptable when approaching a curve with an obstructed view because doing so can create a hazardous situation. In these conditions, drivers cannot see oncoming traffic or obstacles that may be present around the curve. Attempting to overtake another vehicle in such a scenario increases the risk of a head-on collision or other accidents, as it compromises safety by not allowing the driver to make informed decisions regarding the road ahead. Safe driving practices emphasize ensuring clear visibility before executing maneuvers like overtaking, which is why this situation specifically prohibits the action.

In contrast, overtaking may be permissible in other situations, such as on a one-way roadway, where drivers can safely pass without oncoming traffic concerns.