Federal and State Weight Limits Explained
The federal gross vehicle weight limit for commercial motor vehicles on Interstate highways is 80,000 pounds. This limit applies to the combined weight of the tractor, trailer, and cargo. However, this is just one of several weight constraints you must comply with simultaneously. Individual axle weight limits further restrict how weight is distributed across the vehicle.
The federal single-axle weight limit is 20,000 pounds. The tandem-axle limit (two axles spaced 40 to 96 inches apart) is 34,000 pounds. For a typical five-axle tractor-trailer combination, this means: steer axle maximum 12,000 to 14,000 pounds (most steer axles are rated below the federal 20,000 maximum), drive tandem maximum 34,000 pounds, and trailer tandem maximum 34,000 pounds. The sum of these axle limits (12,000 + 34,000 + 34,000 = 80,000) equals the federal GVW limit.
State weight limits can be lower or higher than federal limits on non-Interstate roads. Some states allow higher gross weights on state highways: Michigan allows up to 164,000 pounds on certain roads with additional axles, and several states in the Northeast allow up to 99,000 pounds with permits. Conversely, some states impose lower limits on certain bridges, roads, or during spring thaw seasons when road surfaces are vulnerable.
The bridge formula adds another layer of complexity. It calculates the maximum weight allowed between any two axle groups based on the number of axles and the distance between the outer axles of the group. The purpose is to prevent excessive concentrated weight that could damage bridges. Even if your individual axle weights and gross weight are within limits, the bridge formula can still put you in violation if your axle spacing and weight distribution do not meet the formula requirements.
Understanding the Bridge Formula and How to Calculate It
The Federal Bridge Formula (Formula B) is: W = 500 x (LN/(N-1) + 12N + 36), where W is the maximum weight in pounds, L is the distance in feet between the outer axles of the group, and N is the number of axles in the group. This formula applies to any combination of consecutive axles on your vehicle.
For a standard five-axle tractor-trailer with a 51-foot outer bridge (distance from steer axle to rear trailer axle), the bridge formula allows approximately 80,000 pounds, which matches the federal GVW limit. However, the inner bridge (distance between drive tandem and trailer tandem) is where most bridge formula violations occur.
A common inner bridge of 36 feet allows approximately 60,500 pounds on the four tandem axles. This means the combined weight on your drive tandems and trailer tandems cannot exceed 60,500 pounds even though each tandem individually could carry up to 34,000 pounds (totaling 68,000). The bridge formula restricts you to less than the sum of individual axle limits to protect bridges.
To increase the allowable inner bridge weight, increase the distance between the drive and trailer tandems. Spreading the trailer tandems back or using a longer trailer increases the inner bridge measurement. Many experienced operators know their truck's specific bridge formula limits and adjust trailer tandem position accordingly. A spread of 40 to 43 feet on the inner bridge allows the maximum 68,000 pounds on the four tandems, which combined with a 12,000-pound steer axle equals the 80,000-pound GVW limit.
How to Use Truck Scales and CAT Scales
CAT Scale is the largest network of certified truck scales in North America with over 2,000 locations, primarily at truck stops. Weighing your truck is essential before hitting the road with a new load, after any reload or partial unload, and anytime you are unsure about weight compliance.
To use a CAT Scale: pull onto the scale platform, positioning your steer axle over the first pad, drive tandems over the second pad, and trailer tandems over the third pad. Some scales have only two pads, weighing the front axle group and rear axle group separately. Enter the truck stop, tell the cashier your scale number, and pay the fee ($12 to $15 for an initial weigh, with a free reweigh within 24 hours at any CAT Scale location).
Your scale ticket shows three weights: steer axle weight, drive tandem weight, and trailer tandem weight, plus the gross vehicle weight. Compare each to the legal limits: steer under 12,000 to 14,000 pounds (check your steer axle rating), drives under 34,000, trailer tandems under 34,000, and gross under 80,000. If any weight exceeds its limit, you must redistribute or remove cargo before entering any public road.
CAT Scale offers the Weigh My Truck app that stores your weigh tickets digitally, tracks weight trends across loads, and provides the free reweigh guarantee. If you get a weight ticket at a DOT inspection that differs from your CAT Scale ticket by more than the scale's tolerance, CAT Scale will pay your fine. This guarantee only applies if you used their scale within the past 24 hours and before the inspection.
How to Distribute Weight Correctly
Weight distribution starts before loading. The position of your fifth wheel determines how weight splits between the drive tandems and trailer tandems. Moving the fifth wheel forward shifts weight from the trailer tandems to the drives. Moving it backward shifts weight from the drives to the trailer tandems. Most operators set their fifth wheel position based on the type of freight they commonly haul and fine-tune at the scale.
Trailer tandem position is your other adjustment lever. Sliding trailer tandems forward shifts weight from the trailer axles to the drive axles. Sliding them backward shifts weight from the drives to the trailer tandems. The combined adjustment of fifth wheel position and trailer tandem position gives you precise control over weight distribution.
For a standard 45,000-pound payload in a 53-foot dry van, a balanced distribution puts approximately 12,000 pounds on the steer axle, 33,000 to 34,000 on the drives, and 33,000 to 34,000 on the trailer tandems. Achieving this balance requires the cargo to be loaded with the center of gravity positioned correctly within the trailer. Front-heavy loads push weight onto the drives; rear-heavy loads push weight onto the trailer tandems.
When you cannot control where the shipper loads the freight (which is most of the time), your adjustments at the scale are limited to fifth wheel and tandem position. If the load is so unevenly distributed that you cannot get all axle weights within limits through these adjustments, you need to return to the shipper for a reload. Never drive overweight on any axle; fines range from $1 to $10 per pound over the limit in most states, meaning 2,000 pounds overweight can cost $2,000 to $20,000.
Weigh Station Procedures and PrePass/Bypass Systems
Weigh stations are state-operated facilities where commercial vehicles are checked for weight compliance, safety violations, and credential verification. When a weigh station is open, you are required to enter unless you have an active bypass transponder that signals you to bypass.
PrePass is the most widely used bypass system, with transponders installed in the truck that communicate with weigh station equipment. As you approach an open weigh station, the transponder sends your vehicle identification to the station. If your safety record, credentials, and weight history are satisfactory, you receive a green light to bypass. If your record has issues or you are selected for random inspection, you receive a red light and must enter.
DriveWyze is a smartphone-based bypass system that works similarly to PrePass but uses your phone's GPS and cellular connection instead of a physical transponder. It covers over 800 weigh stations and inspection sites across North America. Both PrePass and Drivewyze require monthly subscriptions ($15 to $25/month) and only work if your safety record and credentials are in good standing.
When you do enter a weigh station, follow these steps: approach at the posted speed (usually 5 to 15 MPH), pull onto the scale as directed, stop when signaled, and wait for the light or display to indicate your weight status. Green means proceed. Red means pull to the inspection area. Keep your CDL, registration, medical card, insurance, and permits readily accessible. Be polite and professional with inspectors; your attitude can influence whether a borderline issue results in a warning or a violation.
Consequences of Overweight Violations and How to Avoid Them
Overweight violations carry severe consequences that escalate with the severity of the violation. Minor overweight (under 2,000 pounds) typically results in a fine of $100 to $500 and may require you to redistribute or offload weight before continuing. Moderate overweight (2,000 to 5,000 pounds) can result in fines of $500 to $5,000, potential out-of-service orders, and CSA points. Severe overweight (5,000+ pounds) triggers fines of $5,000 to $25,000+, mandatory offloading, possible vehicle impoundment, and potential criminal charges in some states.
Beyond fines, overweight violations affect your CSA score under the Vehicle Maintenance BASIC. Repeated violations lead to FMCSA intervention (warning letters, compliance investigations, or operational orders). Brokers and shippers who monitor carrier safety data may refuse to work with carriers who have elevated CSA scores, directly impacting your revenue.
To avoid overweight violations: weigh every load at a certified scale before heading to the highway. If the shipper provides a weight on the BOL, verify it with your own scale ticket, as shipper-provided weights are frequently inaccurate. Know the specific weight limits for every state on your route (some states enforce lower limits on certain roads or during seasonal restrictions). Calculate your empty truck weight so you know your maximum payload before accepting a load.
Keep in mind that fuel weight changes throughout your trip. A full 200-gallon fuel tank weighs approximately 1,400 pounds. If you scale at a truck stop with full tanks and your drives are at 33,800 pounds, you are legal. But if you filled up at a stop 10 miles from the scale and your drives were at 33,500 before fueling, the additional 1,400 pounds of fuel (which sits near the drive axles) pushed you to 34,900, which is 900 pounds over the tandem limit. Account for fuel weight when making weight decisions.
Frequently Asked Questions
Find the Right Services for Your Business
Browse our independent reviews and comparison tools to make smarter decisions about dispatch, ELDs, load boards, and factoring.