What types of vehicles must stop at all railroad crossings?

Vehicles that are required to stop at all railroad crossings include school buses and those carrying hazardous materials. The rationale behind this requirement is primarily safety. School buses transport children, making it crucial for drivers to ensure the area is clear of trains before proceeding. Stopping allows for extra vigilance and ensures that young passengers are kept safe.

For vehicles carrying hazardous materials, the potential consequences of a collision at a railroad crossing can be particularly severe. These types of materials can pose significant risks not only to the occupants of the vehicle but also to emergency responders and the public. Stopping provides an opportunity to assess the situation and avoid catastrophic accidents.

The other types of vehicles listed in the choices either do not have the same safety considerations or legal mandates associated with stopping at railroad crossings. Therefore, the responsibility placed on school buses and hazardous material carriers highlights the importance of precautionary measures in protecting both lives and property.