A safety director is evaluating a 5-axle tractor-semitrailer for a dedicated interstate ro… — Commercial Driver's License (CDL) General Knowledge Exam

A safety director is evaluating a 5-axle tractor-semitrailer for a dedicated interstate route. To avoid citations, the vehicle must strictly comply with all manufacturer ratings and federal statutory weight limits.

Below are the specifications for the vehicle combination:

Manufacturer Ratings

Component	Rating
Tractor Steer Axle (GAWR)	$11,000 \text{ lbs}$
Tractor Drive Tandem (GAWR)	$34,000 \text{ lbs}$
Semitrailer Tandem (GAWR)	$28,000 \text{ lbs}$
Tractor GVWR	$45,000 \text{ lbs}$
Semitrailer GVWR	$60,000 \text{ lbs}$
Tractor GCWR	$82,000 \text{ lbs}$

Certified Empty (Tare) Weights

Unit	Weight
Tractor (uncoupled)	$16,500 \text{ lbs}$
Semitrailer (uncoupled)	$11,500 \text{ lbs}$

Federal Statutory Limits (Interstate)

Limit Type	Maximum Weight
Single Axle	$20,000 \text{ lbs}$
Tandem Axle	$34,000 \text{ lbs}$
Gross Combination Weight	$80,000 \text{ lbs}$

Assuming the cargo can be distributed perfectly to maximize allowable limits, what is the absolute maximum payload (in lbs) this combination can legally carry?

Answer: 45000 lbs

Answer

45,000

The correct maximum payload is determined by identifying the most restrictive weight limit on the vehicle. While the federal gross limit allows up to

80,000 \text{ lbs}

, the sum of the maximum allowable weight for each axle group (restricted by their specific GAWRs) is only

73,000 \text{ lbs}

. Subtracting the total empty weight of

28,000 \text{ lbs}

yields an absolute maximum legal payload of

45,000 \text{ lbs}

Step-by-Step Solution

Calculate the total empty weight of the combination.

28,000 \text{ lbs}

You must know the vehicle's tare weight to subtract from the gross limit to find the payload capacity.

Determine the legal weight limit for each axle group (lower of GAWR or Statutory Limit).

Steer:

11,000 \text{ lbs}

, Drive:

34,000 \text{ lbs}

, Trailer:

28,000 \text{ lbs}

A vehicle can never legally exceed the structural rating (GAWR) set by the manufacturer or the federal legal limit, whichever is stricter.

Sum the maximum allowable axle weights.

73,000 \text{ lbs}

The sum of the individual axle limits establishes the absolute maximum gross weight the vehicle can scale without overloading an axle.

Compare the sum of the axles to the GCWR and Federal Gross Limit to find the most restrictive overall limit.

The

73,000 \text{ lbs}

axle sum governs because it is lower than both

80,000 \text{ lbs}

(Federal) and

82,000 \text{ lbs}

(GCWR).

The absolute maximum legal scale weight is always determined by the lowest bottleneck in the vehicle's specifications.

Subtract the total empty weight from the most restrictive gross limit.

45,000 \text{ lbs}

Maximum payload is the difference between the maximum allowed scale weight and the empty weight of the vehicle.

Key Concept

A commercial vehicle's maximum legal payload is bottlenecked by its most restrictive limit, requiring a driver to compare the overall gross limits, unit-specific GVWRs, and the sum of all individual axle limits (lesser of GAWR or statutory).

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