Combination Vehicles · Driving Combination Vehicles Safely
You are driving a combination vehicle and, after applying the brakes hard, you see in your mirrors that the trailer has begun to swing out of your lane. What is the correct response?
Explanation
A trailer, or jackknife, skid happens when the trailer wheels lock up; the fix is to stop using the brake, letting the wheels regain traction, after which the trailer falls back in line behind the tractor on its own. Reaching for the trailer hand valve is explicitly the wrong move, because trailer-wheel braking is what started the skid, so more of it can only prolong the slide. This is a manual-only technique, topic-scoped to 49 CFR 383.111(c)(3)(i). Braking harder keeps the wheels locked and makes the skid worse rather than better. Sharp opposite steering is not the taught correction for this skid type and risks triggering a second, worse skid.
Source: 49 CFR 383.111(c)(3)(i)
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