Which of the following is a type of protective vehicle?

The correct answer is based on the role of protective vehicles in work zone traffic control. Advanced warning vehicles are specifically designed and equipped to provide essential protection to workers and motorists by alerting them to upcoming work zones and potential hazards. These vehicles typically have signage and flashing lights to enhance visibility and communicate warnings effectively.

They play a crucial role in traffic management by ensuring that vehicles approaching a work zone are informed of changes in traffic patterns and necessary precautions. This proactive approach helps to minimize accidents and maintain a safer environment for both workers and drivers.

In contrast, the other options represent different types of vehicles that do not serve this specific protective function. For instance, hydraulic vehicles are generally associated with construction equipment, reflective refers to materials that improve visibility but do not indicate a type of vehicle, and concrete mixers are specific to transporting concrete but do not provide the warning or protective features associated with advanced warning vehicles.