This sign means:

Question

A three-sided yield sign indicates that you are approaching an intersection where you must wait for vehicles on the other roadway to pass before you proceed. You do not need to come to a complete stop if you are sure that no other vehicles are coming, but you should still always slow down and enter the intersection with caution.

Accepted Answer

Slow down and yield to traffic on the main road when merging.

Answer

Always come to a complete stop.

Answer

Activate your turn signal and proceed into traffic at the usual speed.