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Combination Vehicles Practice Question 38

Required for Class ACombination Vehicles · Question 38

A heavy trailer pushing on the tractor going downhill is called:

• ATailgating
• BTrailer push or coupling stretch
• COff-tracking
• DSurge

Correct answer: B. Trailer push or coupling stretch

Why: When trailer braking lags or the trailer is heavier than the tractor, the trailer pushes on the coupling, contributing to potential jackknife. Apply trailer brakes ahead of tractor brakes when needed.

How this question fits the Combination test

Articulated vehicles fail in unique ways: trailer swing under braking, rearward amplification under steering, and jackknife under loss of traction. Combination Vehicle knowledge is required for any Class A applicant under 49 CFR 383.111.

Study technique for this topic

Walk through the coupling sequence verbally until it's second nature. Know the safe-rolling rearward amplification factor, the difference between trailer service brakes and parking brakes, and what creates the conditions for a tractor jackknife.

Related Combination practice questions

• Q53. The blind spots of a tractor-trailer include:
• Q2. The 'fifth wheel' on a tractor is:
• Q15. To prevent rollover with a high center of gravity, you should:
• Q28. When uncoupling a trailer, the order generally includes:
• Q42. Trailer length affects:

Continue your CDL preparation

The Combination Vehicles portion of the CDL knowledge exam covers more than this single question. Use this site's full Combination Vehicles bank to drill every topic, then test yourself with one of our state-specific practice sets to confirm you are ready for the actual DMV exam in your state. Always check your state's CDL handbook for any local addenda before the test day.

If you are still building your overall CDL foundation, start with the General Knowledge bank — every CDL applicant must pass it — and then work outward to the endorsements you plan to add.