A school bus driver approaches a railroad crossing that has a traffic signal or stop sign positioned on the far side, beyond the tracks. Before committing to the crossing, what must the driver confirm?

AAMVA CDL Manual, Section 10.4.4 (Special Situations), p. 10-8

If a bus commits to a crossing and then has to stop because of a signal or stop sign just beyond it, the rear of the bus could still be sitting on the tracks when a train arrives. Checking the containment area first is what prevents that exact failure mode, which is one of the deadliest school bus crash scenarios.