After stopping for a lowered gate, when may a school bus driver proceed across the tracks?

AAMVA CDL Manual, Section 10.4.2 (Gates), p. 10-8; 49 CFR 383.123(a)(2)(iii) (general knowledge-test topic — railroad crossing laws — does not itself state this operational rule); 49 CFR Part 380, Appendix D, Unit D1.6 (Railroad-Highway Grade Crossings)

Multiple-track crossings and signal timing mean the first visible 'all clear' can be misleading. Requiring both the gates to rise and the lights to stop before moving protects against the common and deadly mistake of treating a passing train as the end of the danger.