What must school buses do at all railroad grade crossings?

At all railroad grade crossings, school buses are required to stop unless otherwise directed. This rule is in place to prioritize the safety of the passengers, particularly children, who are often on school buses. By stopping, the bus driver can ensure that the tracks are clear and that no trains are approaching before proceeding.

Stopping at railroad crossings allows for an assessment of both directions and provides an opportunity for the bus driver to listen for any trains, which is crucial in preventing accidents. This requirement recognizes the increased risk associated with transporting young students and emphasizes the need to take precautions at potential hazards such as railroad crossings.

While the other options suggest varying levels of caution, only the requirement to stop ensures that adequate safety measures are taken at these crossings. This is in line with traffic safety regulations that aim to minimize the risk of collisions between trains and vehicles.