Where may advanced warning signs for additional emphasis be posted?

Answer: C — On the left-hand side of the highway

Advanced warning signs are crucial for preparing drivers for potential hazards in work zones. Posting these signs on the left-hand side of the highway is effective because it provides visibility for drivers in both lanes, allowing them to see the warnings as they approach the work zone. This positioning is particularly important on multi-lane roads where vehicles may be traveling at high speeds. The left side of the highway is typically where drivers expect to see key signage. By being placed in this location, advanced warning signs can effectively capture the attention of all approaching vehicles, ensuring that they are alerted to upcoming changes or dangers, thereby enhancing safety for both motorists and workers in the vicinity.