A combination vehicle has ABS on the trailer only. What effect does this have, and what should the driver do if steering control is lost or a tractor jackknife begins?

AAMVA CDL Manual, Section 6.3.2, p. 6-7

Partial ABS setups, where only the trailer or one axle has it, are common on older or mixed equipment, and the correct emergency response doesn't change. A driver who instinctively brakes harder during a jackknife, instead of easing off, can make the skid significantly worse.