Which vehicles must stop at railroad crossings regardless of the warning signals?

The correct choice emphasizes the specific responsibility placed on school buses and vehicles carrying passengers for hire when approaching railroad crossings. These vehicles are required to stop at all railroad crossings, regardless of the presence of warning signals, for safety reasons.

School buses are tasked with the well-being of children, who may not always be aware of their surroundings. Stopping allows the driver to ensure that the tracks are clear and provides an opportunity for children to safely disembark if necessary. Similarly, vehicles that transport passengers for hire, such as taxis or shuttles, are held to this standard due to the increased risk and responsibility involved in ensuring passenger safety.

This regulation stems from the need to prevent potential accidents, as trains can sometimes arrive unexpectedly, and the risks associated with failing to stop at railroad crossings are particularly high for vehicles that are carrying larger groups of people or vulnerable passengers. By requiring these vehicles to stop, the law promotes heightened awareness and caution at a potentially dangerous intersection.