A bus breaks down with riders aboard. Per the CDL manual, when may the driver tow or push it with passengers still on board?

AAMVA CDL Manual, Section 4.5 (Prohibited Practices), p. 4-3

Towing or pushing a bus full of riders is risky, so this rule limits it to situations where leaving people at the roadside would be more dangerous than keeping them on board for a short move.