Final answer:
School buses must stop at railway crossings under all circumstances to ensure the safety of passengers. Traffic signals at intersections further enhance pedestrian safety and regulate vehicle speed.
Step-by-step explanation:
The question pertains to rules and regulations regarding school bus safety and their mandatory conduct at railway crossings. Under U.S. law and in the interest of pedestrian safety, school buses must stop at railway crossings under all circumstances, which is option b. This law is enforced to ensure the safety of the passengers on the bus, particularly because students are usually the occupants, and to prevent tragic accidents that could occur if a bus were to cross without caution.
A related concern in discussions of road safety is installing traffic signals at intersections to manage vehicle and pedestrian traffic effectively, ensuring pedestrian safety, and reducing the chance of accidents. Traffic signals are particularly beneficial where there is a history of vehicles speeding or other concerns about the safe passage of pedestrians, such as at busy intersections near schools or campuses.