Final answer:
Trains, buses, and commercial vehicles are required to stop at all railroad crossings.
Step-by-step explanation:
The vehicles that are required to stop at all railroad crossings include:
- Trains: Trains, including freight trains and passenger trains, must always stop at railroad crossings to ensure safety.
- Buses: School buses and public transportation buses are also required to stop at railroad crossings.
- Commercial Vehicles: Trucks, tractor-trailers, and other commercial vehicles are required to stop at railroad crossings as well.