Final answer:
A white one-way left-turn arrow over a lane indicates that the lane is solely for making a left turn in the direction of the arrow, helping to guide traffic flow and increase safety.
Step-by-step explanation:
A white one-way left-turn arrow over a lane signifies to drivers that the lane is designated for the exclusive purpose of making a left turn and that this turn should only be made in the direction of the arrow.
This often means that you need to prepare to turn left and that you should not go straight or turn right from this lane. Such signs are used to increase traffic efficiency, enhance safety, and provide clear guidance to drivers, preventing confusion at intersections and reducing the potential for accidents.