Federal regulations limit vehicle size and weight on federal highways. This includes all interstate highways across the country, as well as other federal roads designated within the National Highway System or National Network.
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Federal weight limits of vehicles and axle loading limits are governed by the Federal Bridge Law (FBL), which has four primary rules:
- The maximum weight allowed on a single axle is 20,000 lbs
- The maximum total weight allowed on any two consecutive axles spaced eight or fewer feet apart (like tandem axles) is 34,000 lbs
- The maximum allowed Gross Vehicle Weight (GVW), or the maximum allowed total weight on any group of consecutive axles on a vehicle, is determined by the Federal Bridge Formula (FBF).
- The maximum Gross Vehicle Weight (GVW) on Interstate highways is 80,000 lbs, even when the result of the formula is greater.
The Federal Bridge Formula (FBF)
W = [ ( (LN) / (N - 1) ) + 12N + 36 ]
- W = the maximum allowed total weight in pounds for all axles in the group (rounded to the nearest 500 lbs, and rounding down when right in the middle - i.e. 62,250 lbs rounds to 62,000, while 62,300 lbs rounds to 62,500)
- L = the length or distance in feet (rounded to the nearest foot) from the center of the forward-most axle in the group to the center of the rear-most axle in the group
- N = the total number of axles in the group
Where:
Essentially, the Federal Bridge Formula allows a vehicle to weigh more when there are more axles and/or there is more distance to spread its weight out.
The Federal Bridge Table
For convenience, the Federal Highway Administration published the Federal Bridge Table, which allows one to quickly lookup the federal maximum gross weight on a vehicle or group of consecutive axles, based on number of axles and overall axle length:
For convenience, the Federal Highway Administration published the Federal Bridge Table, which allows one to quickly lookup the federal maximum gross weight on a vehicle or group of consecutive axles, based on number of axles and overall axle length:
Federal Bridge Law Examples
Max GVW: 51,000 lbs
215 in
Example 1: This tandem dump truck has 3 axles and with a 215-inch wheelbase its overall axle length is 20 feet. So according to the Federal Bridge Formula, its total weight (GVW) is limited to 51,000 lbs.
Max GVW: 60,500 lbs
215 in
Example 2: This truck has the same wheelbase and overall axle length as the truck in Example 1, but we've added two axles to make it a quad-axle dump truck with five total axles, which increases its maximum allowed GVW to 60,500 lbs.
Max GVW: 62,500 lbs
250 in
Example 3: Here, we took the quad-axle dump truck from Example 2 and stretched its wheelbase to 250 inches, making its overall axle length 23 feet. This has increased its maximum allowed GVW to 62,500 lbs under the Federal Bridge Law.
Max GVW: 80,000 lbs
250 in
Example 4: This is a 7-axle Super Dump, with the truck having the same 250-inch wheelbase as in Example 3. With the Super Dump, when the trailing axle is deployed, the overall axle length is increased by an additional 12 feet, for 35 feet total, and the maximum allowed GVW is increased to 80,500 lbs by the Federal Bridge Formula (80,000 lbs is the max allowed on Interstate highways, however).
The backbone of our economy &#; the heavy haul trucking services &#; serves as the lifeline for transporting essential goods across long distances. However, with great power comes great responsibility, and ensuring the safety of both drivers and infrastructure requires stringent regulations on truck weight, with a particular focus on axle weight distribution.
These regulations are based on broader area results in a more evenly distributed force, reducing its severity. Adding more axles and space helps accommodate greater load weight on the truck and trailer.
This guide by our team at Cowtown Express explores the intricacies of axle weight limits, navigating through both the federal framework and unique state-specific variations to give you the knowledge you need for smooth and compliant journeys.
Understanding Axle Weight Limits: Federal Bridge Formula
One of the key considerations in heavy haul shipping is understanding axle weight limits. At the federal level, the maximum gross vehicle weight for a semi-truck and trailer combination is set at 80,000 lbs, without the need for a special permit.
This federal limit is meticulously determined using the Federal Bridge Formula, which dictates how this weight is distributed across the truck's axles based on the distance between them. This ensures a balanced weight distribution to effectively minimize stress on bridges and roads.
Federal Bridge Formula
W=500(LN/N-1 + 12N + 36)
Here's the key part: two consecutive sets of tandem axles (think double axles close together) are allowed a maximum gross weight of 34,000 lbs each, but with a catch: the overall distance between the first and last axle in these sets must be at least 36 feet.
In simpler terms, the formula prevents overloading specific sections of a truck, which could put undue stress on bridges and roads. By spreading the weight out more evenly across longer distances, the risk of damage is minimized.
What Are Axle Groups?
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Trucking weight limits are typically categorized based on the type of axle. Steer axles, located at the front of the semi-truck, typically support a total weight of 12,000 to 15,000 lbs between them. A standard semi-truck features two drive axles, with each axle's tires not to exceed 17,000 lbs in weight. This results in a combined total of 34,000 lbs for the two drive axles. Breaking it down, this equates to approximately 6,750 lbs per front tire and 4,250 lbs per drive-axle tire weight.
Federally mandated maximum weights for the National System of Interstate and Defense Highways:
- 80,000 lbs gross vehicle weight.
- 20,000 lbs single axle weight.
- 34,000 lbs tandem axle weight.
Trucking DOT Axle Weight Limits by State
Remember, states have the authority to set stricter limits based on their unique infrastructure and traffic patterns. So, before embarking on your journey, familiarize yourself with the specific axle weight limits for each state you'll be traversing. This knowledge is your shield against hefty fines and ensures you're a responsible citizen of the road.
STATE
SINGLE AXLE
DOUBLE AXLE
TRIDEM
GROSS WEIGHT
ALABAMA
20,000 lbs.
34,000 lbs.
42,000 lbs.
80,000 lbs.
ALASKA
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20,000 lbs.
38,000 lbs.
42,000 lbs.
Per FBF
ARIZONA
20,000 lbs.
34,000 lbs.
Per state weight table
80,000 lbs.
ARKANSAS
20,000 lbs.
34,000 lbs.
50,000 lbs
80,000 lbs.
CALIFORNIA
20,000 lbs.
34,000 lbs.
Undefined
80,000 lbs.
COLORADO
20,000 lbs.
36,000 lbs.
Per FBF
80,000 lbs.
CONNECTICUT
22,000 lbs.
36,000 lbs.
Per FBF
80,000 lbs.
DELAWARE
20,000 lbs.
34,000 lbs.
60,000 lbs.
80,000 lbs.
DISTRICT OF COLUMBIA
21,000 lbs.
37,000 lbs.
Per state weight table
79,000 lbs.
Why Axle Weight Limits Matter
Axle weight limits aren't just bureaucratic hurdles &#; they're critical safeguards for safety and infrastructure. Overloaded trucks pose a triple threat:
- Increased stopping distances: Imagine a loaded elephant trying to stop on a dime &#; that's the risk with overloaded trucks, significantly raising the risk of accidents.
- Tire blowouts: Excessive pressure can lead to tire blowouts, potentially causing loss of control and endangering everyone on the road.
- Bridge and road damage: Those behemoths put immense strain on bridges and pavements, accelerating their deterioration and costing taxpayers dearly in repairs.
Tips for Compliance with Axle Weight Limits
Compliance with axle weight limits and effective truck weight management are essential for a successful and legally sound heavy haul operation. Here's your comprehensive guide to ensuring your journey is smooth and compliant:
#1. Knowledge of Truck Weight Limits
Regardless of your truck's type, whether it's a dry van trailer, a step-deck, or a flatbed trailer, the type of truck involved does not impact the total weight calculation. The actual carrying capacity of your truck is determined by subtracting the combined weight of the truck and trailer from the federal limit of 80,000 lbs.
In practice, this often results in an actual carrying capacity of approximately 43,000 to 48,000 lbs. To consistently adhere to the national maximum gross weight allowed for your semi-truck, your truck's weight, free of a load, should remain under 32,000 lbs. This understanding is fundamental for maintaining compliance, ensuring safety, and efficiently managing the weight of your heavy haul shipments.
#2. Regular Weigh-Ins
Regular weigh-ins are your first line of defense against exceeding axle weight limits. Utilize certified scales both before and after loading your cargo. This practice provides real-time data on your truck's weight, helping you stay within legal boundaries throughout your journey.
#3. Strategic Load Distribution
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Achieving balanced weight across all axles is paramount. Mastering load distribution is a critical skill for heavy haulers. Properly distribute your cargo to ensure that no single axle or axle group carries too much weight. This not only ensures compliance but also enhances the safety and stability of your truck on the road.
#4. Securing Permits
For shipments that exceed standard weight limits, securing the necessary permits is essential. Overweight permits are required when your cargo exceeds the legal weight restrictions set by federal and state regulations. Planning ahead and obtaining these permits in advance can help you avoid fines and potential delays during your trip.
Conclusion
Truck weight restrictions are a common concern for any heavy-haul trucking company. However, these companies prioritize compliance with axle weight regulations to ensure your goods reach their destination safely and efficiently. Regardless of the axle weight limits varying from state to state, they prioritize safety and infrastructure preservation.
Contact us today to receive a quote for your next shipment, knowing that your cargo will be transported with utmost care and in full compliance with legal weight limits.
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