Definition
A loss-of-control condition in which the tractor and trailer fold toward each other at an acute angle.
Practical example
Example: On a slick road, excessive braking can begin a trailer swing or tractor jackknife.
Why it matters
Safe speed, smooth control, space, and proper braking reduce jackknife risk.
Jackknife in CDL training
CDL students should be able to recognize this term, explain it in plain language, and connect it to safe vehicle operation, inspection, licensing, or freight work as applicable. Review the term in context and practice using it during classroom study and hands-on training.
Frequently asked questions
What does Jackknife mean in trucking?
A loss-of-control condition in which the tractor and trailer fold toward each other at an acute angle.
Why should a commercial driver understand Jackknife?
Safe speed, smooth control, space, and proper braking reduce jackknife risk.
This glossary is educational. Always follow current federal and state rules, the vehicle manufacturer’s instructions, and your motor carrier’s procedures.