Final answer:
You should follow the direction of the arrow on a traffic sign that has an arrow with 'only' written below it, as it indicates that the lane is designated only for that direction of travel.
Step-by-step explanation:
When seeing a sign over your lane with an arrow and the word "only" below it, you should go the direction of the arrow. This type of sign indicates that the lane is designated for a specific direction of travel, and you are required to follow that direction. It is imperative for road safety and traffic law compliance to heed these signs and act accordingly. Ignoring such signs could lead to traffic violations or accidents.