Why does the AAMVA manual say the foot brake is safer than the trailer hand valve for normal driving?
Combination Vehicles • Free CDL Practice Question
Regulation
AAMVA CDL Manual, Section 6.2.1 "Trailer Hand Valve," p. 6-4
Why This Matters
Understanding why the foot brake is the safer default reinforces the broader rule: trailer-only braking from the hand valve is what starts a trailer skid, so routing braking force through the full-vehicle foot brake is the safer habit in every driving situation.