Light Vehicle Weight Limits: Discussions of weight compliance for the less-than-Class 8 operators

Dave Elniski, Industry Advisor, Safety & Compliance

This article has been accepted for publication by Western Canada Highway News; their digital editions can be accessed at this link.

I commonly receive requests for help with figuring out weight limits for light vehicles in my role as an AMTA Industry Advisor.  When I say light vehicles, I’m referring to combinations that are significantly lighter than Class 8 tractor-trailers where the manufacturer’s axle and overall weight limits are less than the legal weight limits for the jurisdiction.  Examples of light vehicles for this article include units like a pickup truck pulling a tandem axle bumper-pull dump trailer or a one-ton dually crew cab that occasionally pulls a gooseneck trailer.

My transportation experience is from the Class 8 segment of the industry.  I have found that light vehicle weight management faces a challenge heavy vehicle weight management does not: working with manufacturer limits that are below legal road limits.

The reason why it’s challenging to operate equipment with weight ratings less than the road’s legal limits is because legal weight limits can’t be used to load the vehicle.  A Class 8 tractor-trailer generally has axle and overall weight limits greater than the legal limit for the roadway.  When the vehicle has been loaded to the legal roadway limit, the higher manufacturer weight ratings provide a margin of safety.  Functionally speaking, drivers and carriers of such heavy vehicles need only worry about the road’s legal limit to ensure they are in compliance with the law and operating their vehicles safely.

Finding the Weakest Link

Similar to how a chain’s weakest link determines its strength, the lowest-rated component of a vehicle combination determines its weight limitations.  Here is a list of individual weight limits all drivers and carriers – especially those of light vehicles – need to consider when figuring out their vehicle’s capabilities:

1.Make sure the overall weight of the power unit and trailer(s) is less than the registered GVW.

2.Make sure the overall weight of the power unit and trailer(s) is less than the power unit’s manufacturer’s GCVW or GCWR.

-If there is no listed GCVW/GCWR, contact the manufacturer or dealer.  It is likely a number similar to the vehicle’s GVW plus the towing capacity, but don’t assume.

3.Make sure each individual axle is within its limit, including trailer axles.

4.Make sure the rating of the hitch and hitch components are not exceeded.

5.Make sure the trailer being towed is within the towing capacity of the power unit.

-Ensure the legal and manufacturer requirements for trailer brakes are met.

It isn’t easy to figure out a light vehicle’s weight limits, especially if a company operates many different possible combinations.  I’ll present some best practices that can help: a weight management system and driver weight training.

Weight Management System

The driver of the vehicle is responsible for its safe and legal operation.  However, companies should do more than make drivers responsible for weight management.  Yes, drivers need to understand what they’re doing (I’ll discuss this more in the following driver training section), but a company will perform better in terms of safety and compliance if it has a system in place to help drivers with this task.

A weight management system can consist of three basic components.  The first component is calculating the weight limits for each vehicle and vehicle combination in the fleet.  While this can be a lot of upfront work, it will provide the company with the necessary information for driver training and managing compliance.

The second component of the weight management system is driver training.  I’ll discuss this separately in the next section.

The third component of the weight management system is ongoing system monitoring.  Monitoring weight-related notices and tickets and then taking necessary corrective action is an example of an activity under this part of the system.  Another example is performing periodic paperwork and mechanical inspections of in-use vehicle combinations.  Companies can also routinely confirm correct weight distribution by requiring drivers to weigh their vehicles on a pre-defined, regular basis.

Driver Training

Drivers need to understand how to safely and compliantly operate their vehicle.  Without proper training, they may be left holding the bag during a roadside inspection.  A proactively-minded company should not assume a driver’s licence is an indicator of a thorough understanding of company-specific vehicle weights.

Driver training cannot be done until the company knows the limitations of the vehicles in its fleet (the first part of a weight management system).  Once known, each vehicle can be outfitted with a regularly-updated means of referencing this information (like a paper card or mobile device app), and a proper driver weight training program can be developed specifically for the company’s unique operations.

Training on vehicle weights needs to match the needs of the company.  However, here are some weight-related concepts that should be included:

-Tare weight: the empty or unloaded weight of a vehicle [1]. While Tare is often spelled “TARE”, it is not an acronym and instead a word defined as the difference in weight between an item’s gross weight and its net weight [2].

-GVW: “Gross Vehicle Weight”, the maximum weight of the vehicle; the acronym GVWR (“Gross Vehicle Weight Rating”) is synonymous with GVW.

-Registered GVW: the GVW listed on a commercial vehicle’s certificate of registration. In Alberta, non-buses must be registered with a GVW and cannot be operated on public roadways at more than their certificate weight [3].  The registered GVW can never be less than the Tare weight, but it could be less than the manufacturer’s GVW as long as the vehicle is never operated over the registered GVW; since commercial registration fees typically increase with GVW, a business may be able to save money by selecting a lower registered GVW as long as they never operate over their registration limit [3].

-Manufacturer’s GVW: the maximum GVW of the vehicle according to the engineers that built it; depending on the vehicle, the GVW provided may not include trailers (see GCVW and GCWR).

-GCVW and GCWR: the maximum weight of a vehicle and any trailers being pulled by it. GCVW/GCWR should encompass a power unit’s towing capacity.  It is generally the GVW of the power unit plus the power unit’s towing capacity, but the calculation may not be this simple.  The GCVW/GCWR should be obtained from the manufacturer.

-Towing Capacity: the maximum weight of a trailer that can be safely towed by a vehicle. The manufacturer may also set towing limits for the length, front area, and side profile of a trailer.

-Hitch Capacity: hitches and their components have capacity limits, including overall towing limit, tongue weight limit, and the limits of additional devices like pins and safety chains.

-Axle Weight Ratings: each axle of a vehicle has a maximum weight (trailers, too). Even if a vehicle is under its GVW, no single axle may be over that axle’s limit.  When individual axle limits add to more than the GVW, the vehicle must have at least one axle under limit for the overall vehicle to be within its limits.

An effective weight management system with a solid driver training component will boost the confidence of the company and drivers alike.

Summary

Whether a person is planning to tow a travel trailer behind their personal vehicle or managing a fleet of vehicles, knowing vehicle weight limits is crucial to a safe, compliant experience.  The implementation of a system to manage this task will produce a solid foundation upon which safe and responsible fleet operations can grow.

References

1 – Government of Alberta.  2021.  “Module 4: Weights and Dimensions.”  In Commercial Vehicle Safety Compliance in Alberta.  Accessed online on February 15th, 2022, from https://open.alberta.ca/dataset/c5d46860-b4ba-474e-a466-4185cf0010a4/resource/97203ad0-5e30-4f3c-82aa-f7018edaa014/download/trans-commercial-vehicle-safety-compliance-in-alberta-2021-module-4.pdf

2 – Online Etymology Dictionary.  2022.  “Tare (n.2).”  Accessed February 15th, 2022, from https://www.etymonline.com/word/tare

3 – Information in this section confirmed through conversations between Dave Elniski (author) and private Alberta commercial registry agents referencing their Government of Alberta policies during the month of February, 2022.  Different jurisdictions may have different rules.