During radiography on a bridge above a highway, what should you do if a vehicle stops in an area with a dose rate above 10 mR/hour?

In the context of radiography, particularly when working in proximity to public areas such as highways, safety protocols are paramount. If a vehicle stops in an area where the dose rate exceeds 10 mR/hour, it indicates that the level of radiation exposure could be harmful to individuals who are not equipped or trained to handle such levels of radiation.

Retracting the source immediately is the correct course of action because doing so minimizes the radiation exposure to the occupants of the vehicle and ensures their safety. It is a measure designed to prevent accidental radiation exposure and demonstrates a commitment to safety standards in radiological work. By retracting the source, you effectively reduce the radiation field and limit the risk to those in the vicinity.

In contrast, continuing to work as usual could lead to unnecessary exposure for the vehicle occupants, and notifying nearby workers to stay clear, while important, does not address the immediate risk posed by the exposure to the vehicle's occupants. Taking note of the vehicle's license plate may seem like a precautionary measure, but it does not mitigate the potential radiation hazard in the moment. Therefore, retracting the source is the most responsible and prudent action to ensure safety.