Missouri Truck Weight Limits and Regulations

Operating a commercial motor vehicle in Missouri requires strict adherence to weight regulations enforced by the Missouri Department of Transportation (MoDOT) and the Missouri State Highway Patrol. The state distinguishes weight limits based on the type of roadway, with specific restrictions for the Interstate system compared to the non-Interstate Supplementary system. For most standard commercial configurations, the maximum gross vehicle weight allowed on Missouri Interstates without a permit is 80,000 pounds, provided the vehicle meets the Federal Bridge Formula requirements. Missouri Revised Statutes Chapter 304 governs these limits to prevent premature pavement degradation and ensure structural integrity across the state's 10,000+ bridges. Dispatching heavy loads across the Show-Me State requires precise planning to avoid costly violations at weigh stations like those on I-70 or I-44. DispatchTool helps carriers manage these complexities by providing truck-safe routing that accounts for Missouri-specific bridge weight restrictions and posted limits on secondary routes. By integrating load data with road constraints, users can verify that their gross and axle weights remain compliant before the wheels turn. Create a DispatchTool account to start planning routes that align with Missouri's legal weight standards.

Standard Gross and Axle Weight Limits

On Missouri Interstate highways and designated primary routes, the legal gross vehicle weight limit is 80,000 pounds. Axle weight limits are strictly enforced: a single axle is limited to 20,000 pounds, while a tandem axle group (spaced more than 40 inches but not more than 96 inches apart) is limited to 34,000 pounds. For non-Interstate routes, Missouri allows a slightly higher single axle limit of 22,000 pounds and a tandem axle limit of 36,000 pounds, though the 80,000-pound gross cap remains standard unless the vehicle is operating under a specific exemption or permit. The steering axle is typically limited to the manufacturer's load rating or a maximum of 20,000 pounds.

The Bridge Formula and Axle Spacing

Missouri utilizes the Federal Bridge Formula B to determine the maximum weight allowed on any group of two or more consecutive axles. The formula is expressed as W = 500 [LN/(N-1) + 12N + 36], where W is the maximum weight, L is the distance in feet between the extremes of any group of axles, and N is the number of axles in the group. This ensures that weight is distributed effectively to protect bridge spans. For example, a five-axle tractor-trailer with a 51-foot wheelbase can legally carry the full 80,000 pounds, but shorter combinations may be restricted to 73,280 pounds or less despite having the same number of axles.

Special Limits for the Commercial Zone

Missouri Revised Statute 304.190 establishes 'Commercial Zones' around cities like St. Louis, Kansas City, and Springfield. Within these defined zones, which typically extend 15 to 18 miles from the city limits, trucks are permitted to carry heavier loads on non-Interstate highways. The gross weight limit in these zones increases to 22,400 pounds per axle, provided the total gross weight does not exceed the maximum allowed for the specific vehicle configuration. However, these higher limits do not apply to the Interstate system, where the 80,000-pound cap and standard axle limits are strictly maintained regardless of the zone.

Overweight Permit Fees and Procedures

When a load is non-divisible and exceeds legal limits, a MoDOT Oversize/Overweight permit is required. A single-trip overweight permit costs $15.00 for the permit fee plus an additional 'weight fee' calculated at $20.00 for every 10,000 pounds over the legal limit. For example, a load weighing 90,000 pounds would incur a $20.00 weight fee in addition to the $15.00 base permit fee. Blankets or annual permits are available for specific configurations, such as $100.00 for a multi-trip permit up to 100,000 pounds. Missouri requires all permit applications to be submitted through the MoDOT Carrier Express online portal.

Agricultural and Livestock Exemptions

During the designated harvest season, Missouri law allows for a 10% allowance above the legal weight limits for vehicles hauling agricultural products or livestock from the farm to the first point of processing. This allowance increases the maximum gross weight to 88,000 pounds on non-Interstate highways. It is important to note that this 10% tolerance does not apply to the Interstate system, where the 80,000-pound limit is federally mandated. Drivers must carry proof that they are engaged in agricultural transport and heading to a primary market or processing facility to qualify for this tolerance during a roadside inspection.

Enforcement and Fine Schedules

Weight enforcement is conducted by the Missouri State Highway Patrol at fixed scale houses and mobile units using portable scales. Fines for overweight violations in Missouri are calculated based on the number of pounds over the legal limit. According to MoDOT, if a vehicle is 0 to 500 pounds over, the fine may be minimal, but it escalates quickly: 1,000 to 2,000 pounds over can result in fines of $0.04 per pound, while exceeding the limit by more than 5,000 pounds can result in fines of $0.10 per pound or more plus court costs. Carriers found in violation are often required to offload the excess weight before proceeding, leading to significant delays and secondary costs.

Sources

Missouri Department of Transportation (MoDOT) (2024) — https://www.modot.org/mcs Missouri Revised Statutes Chapter 304 (2023) — https://revisor.mo.gov/main/OneSection.aspx?section=304.180 Federal Highway Administration (FHWA) (2024) — https://ops.fhwa.dot.gov/freight/sw/brdgcalc/index.htm

Frequently asked

What is the maximum weight for a tandem axle in Missouri?

On Missouri Interstates, the tandem axle limit is 34,000 pounds. On non-Interstate highways, the limit is slightly higher at 36,000 pounds per tandem group.

Does Missouri allow 88,000 pounds on the Interstate for grain haulers?

No, the 10% harvest tolerance that allows up to 88,000 pounds only applies to non-Interstate highways; the 80,000-pound limit remains strictly enforced on all Missouri Interstates.

How much does an overweight permit cost in Missouri?

A single-trip permit starts at a $15.00 base fee, with an additional $20.00 charged for every 10,000 pounds over the legal gross weight limit.

Are there specific weight limits for the St. Louis Commercial Zone?

Yes, within the St. Louis Commercial Zone, axle limits increase to 22,400 pounds on non-Interstate routes, though vehicles must still adhere to 80,000 pounds if they enter the Interstate system.

What is the fine for being 5,000 pounds overweight in Missouri?

For a violation of 5,000 pounds over the legal limit, Missouri typically assesses a fine of $0.10 per pound, totaling approximately $500.00 plus applicable court costs and fees.