Final answer:
Three groups of people with authority to direct traffic and override usual controls are police officers, emergency responders, and road workers like construction and maintenance personnel. These individuals are empowered to manage traffic flow for public safety, during emergencies, and for pedestrian protection.
Step-by-step explanation:
The three groups of people who have the authority to direct traffic and override signs and signals are police officers, emergency responders, and certain road-related workers like construction and road maintenance workers. Police officers exert authority based on their role in enforcing the law and ensuring public safety. For instance, a citizen who observes the flashing lights of a police car will usually comply with the officer's directions readily, recognizing the officer's authority to control traffic and issue citations if necessary.
Emergency responders, such as firefighters or paramedics, may also direct traffic during an emergency situation to ensure quick and safe access to the scene. Similarly, construction and road maintenance workers are often granted the authority to manage traffic through or around a work zone for the safety of both the workers and the motorists.
Pedestrian safety is another essential consideration, especially in areas with high foot traffic such as school zones. A traffic signal improves pedestrian safety by allowing people to cross at designated times, thereby reducing the risks associated with dodging vehicles. Lastly, the number of accidents at an intersection is a critical factor that may necessitate these individuals to take control over traffic signals in the interest of public safety.