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Difficulty: Very hardWeight Definitions and Limits (GVWR, GCWR, Axle Weights)

A driver is preparing to haul a load on an interstate highway using a 3-axle straight truck towing a 2-axle pup trailer. The vehicle combination has the specifications listed below.

Truck Specifications:
- Steer Axle GAWR: 14,000 lbs14,000 \text{ lbs}
- Drive Tandem GAWR: 44,000 lbs44,000 \text{ lbs}
- Gross Vehicle Weight Rating (GVWR): 58,000 lbs58,000 \text{ lbs}
- Empty Weight (Tare): 24,000 lbs24,000 \text{ lbs}
- Gross Combination Weight Rating (GCWR): 78,000 lbs78,000 \text{ lbs}

Trailer Specifications:
- Tandem Axle GAWR: 28,000 lbs28,000 \text{ lbs}
- Gross Vehicle Weight Rating (GVWR): 28,000 lbs28,000 \text{ lbs}
- Empty Weight (Tare): 8,000 lbs8,000 \text{ lbs}

Assuming the payload can be perfectly distributed to maximize allowable weight, what is the maximum legal payload this combination can carry without violating any federal interstate weight limits or manufacturer ratings?

  1. A
    48,000 lbs48,000 \text{ lbs}
  2. 44,000 lbs44,000 \text{ lbs}Answer
  3. C
    54,000 lbs54,000 \text{ lbs}
  4. D
    46,000 lbs46,000 \text{ lbs}

Answer

44,000 lbs44,000 \text{ lbs}
The correct payload is found by establishing the lowest binding limit for each axle group, summing them to find the maximum possible gross weight, and subtracting the tare weight. The truck is limited to 48,000 lbs48,000 \text{ lbs} because the federal interstate limit restricts its tandem axle to 34,000 lbs34,000 \text{ lbs}. The trailer is limited to 28,000 lbs28,000 \text{ lbs} by its GAWR. Summing these yields a maximum gross weight of 76,000 lbs76,000 \text{ lbs} (which safely falls under the 78,000 lbs78,000 \text{ lbs} GCWR limit). Subtracting the 32,000 lbs32,000 \text{ lbs} total tare weight leaves 44,000 lbs44,000 \text{ lbs} for allowable payload.

Step-by-Step Solution

1
Identify the binding weight limit for the truck's steer axle.
Maximum legal weight is 14,000 lbs14,000 \text{ lbs}.
The manufacturer GAWR (14,000 lbs14,000 \text{ lbs}) is lower than the standard federal single axle limit (20,000 lbs20,000 \text{ lbs}).
2
Identify the binding weight limit for the truck's drive tandem axle.
Maximum legal weight is 34,000 lbs34,000 \text{ lbs}.
The federal tandem axle limit (34,000 lbs34,000 \text{ lbs}) supersedes the manufacturer GAWR (44,000 lbs44,000 \text{ lbs}) on interstate highways.
3
Calculate the maximum allowable weight for the truck itself.
14,000+34,000=48,000 lbs14,000 + 34,000 = 48,000 \text{ lbs}.
The sum of the binding axle limits (48,000 lbs48,000 \text{ lbs}) restricts the truck below its stated GVWR of 58,000 lbs58,000 \text{ lbs}.
4
Identify the binding weight limit for the trailer's tandem axle.
Maximum legal weight is 28,000 lbs28,000 \text{ lbs}.
The manufacturer GAWR/GVWR (28,000 lbs28,000 \text{ lbs}) is lower than the federal tandem limit (34,000 lbs34,000 \text{ lbs}).
5
Determine the maximum legal gross combination weight.
48,000 (truck)+28,000 (trailer)=76,000 lbs48,000 \text{ (truck)} + 28,000 \text{ (trailer)} = 76,000 \text{ lbs}.
This sum must be compared against the manufacturer GCWR (78,000 lbs78,000 \text{ lbs}) and federal maximum gross (80,000 lbs80,000 \text{ lbs}). The lowest value (76,000 lbs76,000 \text{ lbs}) is the absolute limit.
6
Calculate the maximum payload.
76,000 (max gross)−32,000 (total tare)=44,000 lbs76,000 \text{ (max gross)} - 32,000 \text{ (total tare)} = 44,000 \text{ lbs}.
Payload is the maximum allowable combination weight minus the empty weight of both vehicles (24,000+8,000=32,000 lbs24,000 + 8,000 = 32,000 \text{ lbs}).

Key Concept

Determining maximum legal payload requires evaluating manufacturer ratings (GAWR, GVWR, GCWR) against federal interstate limits (single axle, tandem axle, gross) and applying the most restrictive constraint at every component level.
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Topics

Weight Definitions and Limits (GVWR, GCWR, Axle Weights)

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