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CDL Combination Vehicles Test

Antilock brakes on trailers: practice questions

Our CDL Combination bank has 13 questions on this topic. Here are 5 of them with answers; the full mock exam draws from every topic, like the real one.

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Question 1

How can you check whether an older trailer has ABS?

  1. Look for a red ABS sticker on the trailer's nose near the glad hands
  2. Check for a third glad hand
  3. Press the brake and listen for clicks
  4. Look underneath for the ECU and wheel speed sensor wires
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D. Look underneath for the ECU and wheel speed sensor wires — For units built before the required date, look under the vehicle for the ECU and wheel speed sensor wires coming from the back of the brakes (CDL Manual 6.3.1)

Question 2

Which statement about ABS on a combination vehicle is true?

  1. It lets you follow other vehicles more closely on dry, clear roads
  2. It lets you take curves at higher speed
  3. It lets you skip brake adjustment checks
  4. It won't let you drive faster or follow more closely
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D. It won't let you drive faster or follow more closely — ABS won't allow you to drive faster, follow more closely, or drive less carefully (CDL Manual 6.3.2)

Question 3

Trailers and converter dollies built on or after what date must have ABS?

  1. March 1, 1997
  2. January 1, 1994
  3. March 1, 1998
  4. January 1, 2001
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C. March 1, 1998 — All trailers and converter dollies built on or after March 1, 1998 are required to have ABS (CDL Manual 6.3.1)

Question 4

Your trailer's ABS lamp stays on. What braking ability do you still have?

  1. Normal braking; get the ABS serviced soon
  2. Only the tractor's brakes, until the trailer ABS is repaired
  3. Only the trailer's spring brakes
  4. No trailer brakes until repaired
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A. Normal braking; get the ABS serviced soon — If your ABS malfunctions, you still have regular brakes. Drive normally, but get the system serviced soon (CDL Manual 6.3.2)

Question 5

How should you brake a tractor-trailer with ABS on the tractor, trailer or both?

  1. The same way, using only the force needed to stop safely
  2. Pump the brakes when ABS is on both units so each one can react
  3. Brake harder when only the trailer has ABS
  4. Rely on the hand valve when the tractor has ABS
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A. The same way, using only the force needed to stop safely — Brake the same way regardless of whether you have ABS on the tractor, the trailer or both; use only the force necessary (CDL Manual 6.3.2)

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