• 99 questions

CDL Combination Practice Test on Fifth Wheels and Trailer Brakes

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From what build date must a semitrailer with ABS carry an exterior ABS malfunction indicator lamp?

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Unofficial practice questions, not affiliated with the FMCSA or any state licensing agency. Bank checked October 3, 2026.

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All 99 questions

Fifth wheels and kingpins 15

  • A fifth wheel is designed to be readily separable. How must its locking devices work under 49 CFR 393.70(b)(2)? 49 CFR 393.70(b)(2)
  • Besides brackets and bolts, what must the installation of the lower half of a fifth wheel include? 49 CFR 393.70(b)(1)(i)
  • How does 49 CFR 393.5 describe a trailer kingpin? 49 CFR 393.5
  • How must the lower half of a fifth wheel be secured to the frame of a truck tractor under 49 CFR 393.70(b)(1)? 49 CFR 393.70(b)(1)(i)
  • How securely must the upper half of a fifth wheel be fastened to the motor vehicle that carries it? 49 CFR 393.70(b)(1)(ii)
  • The locking mechanism of a fifth wheel must prevent the two halves from separating unless what happens? 49 CFR 393.70(b)(2)
  • Through which part of a semitrailer do the neck and collar of the kingpin extend, under 49 CFR 393.5? 49 CFR 393.5
  • Under 49 CFR 393.70(b)(3), the position of the lower half of a fifth wheel must not unduly interfere with what? 49 CFR 393.70(b)(3)
  • What does 49 CFR 393.70(b)(3) require of where the upper half of a fifth wheel sits on the semitrailer? 49 CFR 393.70(b)(3)
  • What is a fifth wheel under 49 CFR 393.5? 49 CFR 393.5
  • What may the installation of a fifth wheel not do to the frame of the towing vehicle? 49 CFR 393.70(b)(1)(i)
  • What must every fifth wheel assembly have under 49 CFR 393.70(b)(2)? 49 CFR 393.70(b)(2)
  • Where may the manual release for a fifth wheel locking mechanism be located? 49 CFR 393.70(b)(2)
  • Where must the lower half of a fifth wheel be located on the towing vehicle under 49 CFR 393.70(b)(3)? 49 CFR 393.70(b)(3)
  • Which parts make up the upper coupler assembly of a semitrailer under 49 CFR 393.5? 49 CFR 393.5
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Coupling inspection 16

  • A driver is preparing to haul an intermodal container chassis. Which coupling part does 49 CFR 392.7(b) put on the inspection list? 49 CFR 392.7(b)
  • A driver takes intermodal equipment out on the road. What does 49 CFR 392.7(b) presume about that driver? 49 CFR 392.7(b)
  • A sliding fifth wheel has play between the slider bracket and the slider base. How much movement fails the periodic inspection? 49 CFR Part 396, Appendix A, 2.a(3)(c)
  • Cracks in the fifth wheel plate fail the periodic inspection. Which cracks are excepted? 49 CFR Part 396, Appendix A, 2.a(4)(e)
  • During a periodic inspection, how much movement between the components that mount a fifth wheel to the frame fails the vehicle? 49 CFR Part 396, Appendix A, 2.a(1)(b)
  • How far must a driver go when checking the service brake components of intermodal equipment under 49 CFR 392.7(b)? 49 CFR 392.7(b)
  • How much horizontal movement between a fifth wheel's pivot bracket pin and its bracket fails the periodic inspection? 49 CFR Part 396, Appendix A, 2.a(2)(c)
  • How much horizontal movement between the upper and lower fifth wheel halves fails the periodic inspection? 49 CFR Part 396, Appendix A, 2.a(4)(a)
  • Section 392.7(a) lists parts a driver must be satisfied are in good working order before driving. Which entries concern the link between tractor and trailer? 49 CFR 392.7(a)
  • What fails the mounting plates and pivot brackets of a fifth wheel, apart from missing fasteners and a loose pivot pin? 49 CFR Part 396, Appendix A, 2.a(2)(b)
  • When do missing, broken or deformed fifth wheel locking parts fail the periodic inspection? 49 CFR Part 396, Appendix A, 2.a(4)(f)
  • Which condition of the fifth wheel operating handle fails a periodic inspection under Appendix A to Part 396? 49 CFR Part 396, Appendix A, 2.a(4)(b)
  • Which fifth wheel fastener condition fails a periodic inspection under Appendix A to Part 396? 49 CFR Part 396, Appendix A, 2.a(1)(a)
  • Which of these is on the 49 CFR 392.7(b) inspection list for intermodal equipment? 49 CFR 392.7(b)
  • Which slider defect fails a sliding fifth wheel at the periodic inspection? 49 CFR Part 396, Appendix A, 2.a(3)(b)
  • With the semitrailer coupled, light shows through from side to side between the upper and lower coupler. What does that mean at a periodic inspection? 49 CFR Part 396, Appendix A, 2.a(4)(d)

Trailer brakes, surge brakes and ABS 22

  • A power unit is equipped to tow an air braked trailer. What must it supply to the trailer's ABS to pass the periodic inspection? 49 CFR Part 396, Appendix A, 1.l(5)
  • A semitrailer may go without brakes under 49 CFR 393.42(b)(3) only if its gross weight is no more than what figure? 49 CFR 393.42(b)(3)
  • A semitrailer was built on or after March 1, 2001. Besides a circuit that signals a trailer ABS malfunction, what must it have? 49 CFR 393.55(d)(3)
  • A surge braked trailer is loaded beyond its GVWR. Which figure must be used to check the surge brake weight ratio? 49 CFR 393.48(d)(3)
  • A trailer has a GVWR of 10,000 pounds and surge brakes. How heavy may its GVWR be compared with the towing vehicle's GVWR? 49 CFR 393.48(d)(1)(i)
  • A trailer has a GVWR of 16,000 pounds and surge brakes. What weight ratio applies under 49 CFR 393.48(d)(1)(ii)? 49 CFR 393.48(d)(1)(ii)
  • A trailer has electric brakes. Which breakaway defect fails it at the periodic inspection? 49 CFR Part 396, Appendix A, 1.i(2)
  • A truck has hydraulic brakes but tows a trailer with air brakes. What must the truck have under 49 CFR 393.51(c)? 49 CFR 393.51(c)
  • A truck tows a trailer with vacuum brakes. Besides the single control that works all brakes of the combination, what must the truck have? 49 CFR 393.43(c)
  • A truck tractor was built on or after March 1, 2001. What must its ABS malfunction circuit be able to do for the trailer? 49 CFR 393.55(d)(2)
  • Does the second emergency control on a truck towing a vacuum braked trailer have to give graduated braking? 49 CFR 393.43(c)
  • From what build date must a semitrailer with ABS carry an exterior ABS malfunction indicator lamp? 49 CFR 393.55(e)
  • From what build date must an air braked semitrailer have an antilock brake system? 49 CFR 393.55(c)(2)
  • The manufacturer's GVWR label is missing from a trailer with surge brakes. What may be used to work out the weight ratio? 49 CFR 393.48(d)(2)
  • Must the automatic and manual means of applying the trailer emergency brakes be separate devices? 49 CFR 393.43(b)
  • On coiled brake tubing between tractor and trailer, what is the spring guard at each end for? 49 CFR 393.45(c)
  • To which air braked tractors do the antilock brake items of Appendix A to Part 396 apply? 49 CFR Part 396, Appendix A, 1.l, footnote 2
  • Under 49 CFR 393.41(c)(1), what must the parking brake system of every combination of motor vehicles be able to do? 49 CFR 393.41(c)(1)
  • What is a surge brake under 49 CFR 393.5? 49 CFR 393.5
  • What is the heaviest trailer on which 49 CFR 393.48(d) allows surge brakes? 49 CFR 393.48(d)(1)
  • Which towed vehicle is excused from the rule that all brakes must be capable of operating? 49 CFR 393.48(c)(1)
  • Which trailers fall outside the single application valve rule of 49 CFR 393.49? 49 CFR 393.49(c)

Trailer lamps, conspicuity and rear guards 21

  • A pole trailer's load stands higher than its lamps. When may the pole trailer go without rear identification lamps? 49 CFR 393.11, Table 1, footnote 7
  • A semitrailer built in 1990 is 96 inches wide with a GVWR of 60,000 pounds. How wide must its retrofit retroreflective sheeting be? 49 CFR 393.13(b)
  • A truck tractor is towing a semitrailer. Does the rear of the tractor need a license plate lamp, according to Table 1 of 49 CFR 393.11? 49 CFR 393.11, Table 1, footnote 11
  • How close to the side extremities of a semitrailer must the horizontal member of its rear impact guard reach? 49 CFR 393.86(a)(2)
  • How high above the road must the centerline of the side sheeting on a retrofitted trailer be, measured with the trailer empty? 49 CFR 393.13(c)(1)
  • How high must the rear side marker lamps be mounted on a semitrailer built on or after March 1, 1979? 49 CFR 393.11, Table 1, footnote 4
  • How high off the ground may the bottom edge of a semitrailer's rear impact guard be under 49 CFR 393.86(a)(3)? 49 CFR 393.86(a)(3)
  • How long must a semitrailer be before Table 1 of 49 CFR 393.11 requires intermediate side marker lamps? 49 CFR 393.11, Table 1
  • How many rear identification lamps does Table 1 of 49 CFR 393.11 require on a semitrailer 80 inches or more wide, and in what color? 49 CFR 393.11, Table 1
  • How short must a trailer be to go without front side marker lamps and front side reflex reflectors? 49 CFR 393.11, Table 1, footnote 16
  • May red retroreflective sheeting run along the sides of a trailer retrofitted under 49 CFR 393.13? 49 CFR 393.13(b)
  • On an older trailer retrofitted under 49 CFR 393.13, how much of each side must the sheeting cover? 49 CFR 393.13(c)(1)
  • What color are the intermediate side marker lamps on a long semitrailer? 49 CFR 393.11, Table 1
  • What must go on the upper rear corners of the body of an older trailer retrofitted with sheeting under 49 CFR 393.13? 49 CFR 393.13(c)(3)
  • When are two turn signals required on the rear of a truck tractor, under footnote 2 to Table 1 of 49 CFR 393.11? 49 CFR 393.11, Table 1, footnote 2
  • When must a vehicle's hazard warning flashers be capable of flashing, under footnote 12 to Table 1? 49 CFR 393.11, Table 1, footnote 12
  • Which of these trailers is excepted from the rear impact guard requirements of 49 CFR 393.86(a)? 49 CFR 393.86(a)(1)
  • Which rear impact guard attachment defect fails a newer semitrailer at the periodic inspection? 49 CFR Part 396, Appendix A, 15.a(2)
  • Which semitrailers must carry a rear impact guard that meets FMVSS No. 223 under 49 CFR 393.86(a)(1)? 49 CFR 393.86(a)(1)
  • Which trailers are excepted from the conspicuity requirement of 49 CFR 393.11(b)? 49 CFR 393.11(b)
  • Which trailers must carry conspicuity material, meaning retroreflective sheeting or reflex reflectors, under 49 CFR 393.11(b)? 49 CFR 393.11(b)

Length, width and weight 7

  • A five-axle tractor-semitrailer has two sets of tandem axles. When may each set carry 34,000 pounds under the bridge formula exception? 23 CFR 658.17(e)
  • How far apart are the axles that count as a tandem under the tandem axle weight definition in 23 CFR 658.5? 23 CFR 658.5
  • On the National Network, what is the shortest length limit a state may impose on a semitrailer in a truck tractor-semitrailer combination? 23 CFR 658.13(b)(1)
  • What is the maximum gross vehicle weight on the Interstate System under 23 CFR 658.17(b)? 23 CFR 658.17(b)
  • What is the maximum gross weight on tandem axles on the Interstate System? 23 CFR 658.17(d)
  • What width limit must a state apply to vehicles on the National Network under 23 CFR 658.15? 23 CFR 658.15(a)
  • Which of these is excluded when the width of a commercial motor vehicle is measured under 23 CFR 658.16? 23 CFR 658.16(b)(1)

Class A license and training 18

  • A driver has held a CDL since 2010. Must that driver be retested to see whether the no tractor-trailer restriction applies? 49 CFR 383.153(g)
  • A driver with a valid Class B CDL is training for Class A. Which theory curriculum may that driver complete under Appendix A to Part 380? 49 CFR Part 380, Appendix A
  • A skills test is taken in a tractor-trailer. What does 49 CFR 383.113(a)(1)(ix) add to the pre-trip inspection skills? 49 CFR 383.113(a)(1)(ix)
  • A truck tractor is driven bobtail, towing nothing. How does the exception in the GCWR definition treat the tractor's GCWR? 49 CFR 383.5
  • The CFR names off-tracking once in the required driving skills of 49 CFR 383.113(c). What must the applicant show? 49 CFR 383.113(c)(5)
  • Combination vehicle knowledge under 49 CFR 383.111(c) has three areas. Which set is it? 49 CFR 383.111(c)
  • How is gross combination weight rating (GCWR) found under 49 CFR 383.5? 49 CFR 383.5
  • How many hours of behind-the-wheel instruction does the Class A training curriculum require? 49 CFR Part 380, Appendix A
  • In what vehicle must Class A behind-the-wheel training be conducted? 49 CFR Part 380, Appendix A
  • May a simulation device be used for Class A behind-the-wheel training? 49 CFR Part 380, Appendix A
  • Public road skills A3.8 through A3.12, which include night operation and skid control, are handled how in Class A training? 49 CFR Part 380, Appendix A
  • The third combination vehicle knowledge area is general operating practices and procedures. What does 49 CFR 383.111(c)(3) list under it? 49 CFR 383.111(c)(3)
  • What does restriction code O mean on a CDL, under 49 CFR 383.153(a)(10)? 49 CFR 383.153(a)(10)(iv)
  • What does the vehicle inspection knowledge area for combination vehicles cover, under 49 CFR 383.111(c)(2)? 49 CFR 383.111(c)(2)
  • What is a truck tractor under 49 CFR 390.5T? 49 CFR 390.5T
  • What marks a semitrailer in the definition in 49 CFR 390.5T? 49 CFR 390.5T
  • Which coupling does the coupling and uncoupling knowledge area in 49 CFR 383.111(c)(1) name? 49 CFR 383.111(c)(1)
  • Which loads is a pole trailer built to carry, under 49 CFR 390.5T? 49 CFR 390.5T

How this list was compiled: Written from the Electronic Code of Federal Regulations. Title 49: Parts 380 (Appendix A), 383, 390, 392, 393 and 396 (Appendix A) at https://www.ecfr.gov/current/title-49, text in force on 2026-10-01. Title 23: Part 658 at https://www.ecfr.gov/current/title-23/part-658, text in force on 2026-10-01. Both checked 2026-10-03. Each question names its section. Licence: Own work. Questions, answer choices and explanations were written for this site from the regulation text; nothing is copied from a state CDL manual, the AAMVA test item pool or another practice test.

How it works

This unofficial CDL combination practice test asks 99 questions on federal text, checked 3 October 2026: fifth wheels, coupling defects, trailer and surge brakes, and trailer lamps. The coupling sequence, off-tracking and rollover handling are left to state manuals.

Read the full guide

How this Class A CDL practice test sits against 383.111(c)

49 CFR 383.111(c) names three knowledge areas for combination vehicles. Four topics serve them from 49 CFR 393.70, the Part 393 brake and lamp rules and Appendix A to Part 396. Two go past that list: 18 questions on the Class A license and 7 on size and weight limits in 23 CFR Part 658.

Working through this combination CDL practice test

Questions come ten to a round, and trailer brakes is the largest topic at 22. Pick one topic under More options once a round ends. Exam mode asks 25 questions and passes at 20 right, the 80 percent in 49 CFR 383.135.

  • Appendix A to Part 396 fails a fifth wheel at more than 1/2 inch of horizontal movement between its halves.
  • Surge brakes are allowed only under 20,001 pounds GVWR, at 1.75 or 1.25 times the towing vehicle's rating (393.48(d)).
  • Missed questions wait under More options after each round until you get them right.

Questions and answers

What is on the combination CDL test?

The three areas in 49 CFR 383.111(c): coupling and uncoupling a tractor and semi-trailer, the inspection points that only a combination has, and operating practices, which include air brakes. The regulation lists the areas, not the questions.

Is this the only CDL practice test combination drivers need?

No. 49 CFR 383.111(a) asks every commercial driver for general knowledge too, and 383.95(a) puts an air brake restriction on anyone who fails the air brake part of the knowledge test. The coupling sequence and rollover handling are in your state CDL manual.

What does restriction O on a Class A CDL mean?

No tractor-trailer. Under 49 CFR 383.95(d) a state adds it when the skills test is taken in a Class A combination joined by a pintle hook or another non-fifth wheel connection. Removing it means retaking all three skills tests (383.135(b)(8)).

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