If a reduced speed limit in a highway work zone is at least 10 MPH less than the posted limit, when must a warning sign be erected?

The correct answer regarding the requirement for placing a warning sign when a highway work zone has a reduced speed limit at least 10 MPH less than the posted limit is 600 feet in advance. This distance is established to provide adequate notice to drivers, allowing them sufficient time to slow down and safely respond to the changes in speed limits due to work zone conditions.

By placing the warning sign 600 feet in advance, it ensures that motorists have enough time to adjust their speed and be aware of the upcoming work zone, which is essential for the safety of both the motorists and workers on the highway. This practice is part of standard traffic management strategies aimed at minimizing accidents and enhancing safety in areas where construction or maintenance is taking place.