Applying the AAMVA manual's "If it won't fit, don't commit!" guidance, what should a school bus driver do when there is not enough containment area beyond a railroad crossing to fully clear the tracks?

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

This is the enforcement half of the containment-area rule: checking the space only matters if the driver is willing to hold back when the space isn't there. It turns a measurement into a concrete go/no-go decision that keeps the bus off the tracks.