A bus pre-trip inspection requires spare electrical fuses to be on board unless which condition is met?

AAMVA CDL Manual Section 4.1.1, p.4-1

Electrical failures can disable lights, signals, or other safety systems mid-route. Spare fuses let a driver restore a failed circuit without pulling the bus from service, which is why the rule only waives this requirement when a circuit breaker, a resettable alternative, is already built in.