Antilock Brakes (ABS)
8 free questions, part of the Combination Vehicles CDL practice test
ABS on a combination vehicle does not shorten your stopping distance, it keeps the wheels from locking up so you can keep steering control while braking hard. Trailers and converter dollies built on or after March 1, 1998 are required to have ABS, with a malfunction lamp that tells you when the system is not working. ELDT.io's free bank has 8 antilock brake questions, grounded in 49 CFR 393.55(c)(2), 571.121, and 383.111(b)(7)(ii).
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Start Class A CDL Theory ($15)Questions about Antilock Brakes (ABS)
Does ABS let me stop faster or brake harder?
No. ABS does not add brake pressure or shorten stopping distance, it only keeps wheels from locking so you keep steering control. Brake the same way you always would and drive to conditions.
What does it mean if only the trailer has ABS, not the tractor?
The trailer's wheels are protected from lockup, but the tractor's wheels are not, so you can still lose steering control or start a tractor jackknife even with working trailer ABS. If that happens, ease off the brakes to regain control.
What should I do if the ABS malfunction lamp comes on?
Keep driving and braking normally, then have the system checked at the next opportunity. The lamp means you have lost the anti-lock function, not your conventional brakes.