Before driving a vehicle equipped with a dual air brake system, how much minimum air pressure should you allow the compressor to build in BOTH the primary and secondary systems?

AAMVA CDL Manual, Section 5.2 (Dual Air Brake), p. 5-5. (49 CFR 383.111(b)(4) requires knowledge of 'implications of low air pressure readings' as a topic area but does not itself specify a 100 psi minimum build-up figure; that specific number comes from

Starting a trip without adequate pressure in both circuits risks an in-service low-air event. Waiting for both gauges to reach at least 100 psi before moving is a simple, required pre-drive check that prevents being caught with insufficient reserve air.