What action must a motorist take when making a left turn at a controlled intersection?

When making a left turn at a controlled intersection, yielding to oncoming traffic is essential for ensuring safety. This action is necessary because vehicles approaching from the opposite direction may be traveling straight through the intersection or making their own left turns. By yielding, the motorist allows these oncoming vehicles to pass, preventing potential collisions.

While signaling and adhering to traffic control signals are also important, they do not replace the need to yield. A motorist should signal their intention to turn and wait for appropriate traffic conditions to make the turn safely. However, simply signaling without yielding to oncoming traffic could lead to dangerous situations. Therefore, yielding to oncoming traffic is the critical step in making a safe left turn at a controlled intersection.