April 25, 2002		2002-R-0441
CONNECTICUT AND FEDERAL MAXIMUM ALLOWABLE TRUCK WEIGHTS
By: James J. Fazzalaro, Principal Research Analyst

You asked for a comparison of Connecticut's maximum allowable truck weights and those under federal law. Specifically, you wanted to know if Connecticut's maximum weights, particularly those that apply to axles and the “Bridge Formula” are more restrictive than the federal limits.

SUMMARY

The Connecticut “Bridge Formula” and the federal formula are one and the same. Under Connecticut law, maximum gross weights for commercial vehicles are determined by applying either specific state statutory maximum weights for the vehicle configuration or the Federal Bridge Formula. The bridge formula determines the maximum allowable weight for a vehicle based on the total number of axles it has and the distance between its axle groups (its wheelbase). Thus, for example, a three-axle vehicle might qualify for no more than 53,800 pounds gross weight under the statutory standard but be as much as 60,000 pounds under the bridge formula as long as the wheelbase was at least 32 feet.

Connecticut's maximum allowable axle weights, which are the same under either gross weight option, are actually less restrictive (allow more weight) than the federal maximum axle weights. When maximum truck weights were adopted in federal law as mandatory for application on the Interstate Highway System and certain related highways, states, like Connecticut, that already had higher axle weight limits in effect at the time of adoption of the federal limits, were allowed to retain them through so-called “grandfather” rights. Thus, in Connecticut, a truck can carry up to 22,400 pounds on a single axle and 36,000 pounds on axles spaced less than six feet apart (tandem axles) compared to 20,000 pounds and 34,000 pounds respectively under the federal maximums. Refuse collection vehicles have a special exception for up to 7,000 pounds additional weight on their rear axles but it applies only if they are not using the Interstate Highway System.

STATE MAXIMUM ALLOWABLE TRUCK WEIGHTS (CGS § 14-267a and 14-269)

Maximum Allowable Gross Vehicle Weights

Connecticut law specifies a maximum allowable gross weight for any commercial vehicle according to its number of axles and vehicle configuration (straight truck or vehicle combination), but, in most cases, provides an alternative for calculating the maximum allowable gross weight by means of the Federal Bridge Formula. The practical difference is that a slightly higher gross weight is possible under the formula in many instances as long as the vehicle meets its axle and wheelbase requirements.

Depending on a vehicle's configuration and total number of axles, the maximum allowable gross weights possible under Connecticut law are shown in Table 1.

Table 1. Maximum Allowable Commercial Vehicle Gross Weights in Connecticut

Two-axle Vehicle

● 32,000 pounds (no axle weight restrictions) ● 36,000 pounds with axle weights limited to 18,000 pounds maximum ● Option to use the Federal Bridge Formula for up to 40,000 pounds ● 40,000 pounds if a four-wheel construction vehicle operating within 25 miles of the construction site

Three-axle Vehicle (Straight Truck—Not a Tractor-Trailer Combination

● 53,800 pounds ● Option to use the Federal Bridge Formula for up to 60,000 pounds

Three-axle Combination of Vehicle and Trailer or Semitrailer

● 58,400 pounds ● Option to use the Federal Bridge Formula for up to 60,000 pounds

Four-axle Vehicle Engaged in Construction Work or Transporting Material or Equipment to a Construction Site

● 73,000 pounds

Four-or-more-axle Straight Vehicle or Vehicle-Trailer Combination

● 67,400 pounds if the wheelbase is less than 28 feet ● 73,000 pounds if the wheelbase is 28 feet or more

Five-or-more-axle Straight Vehicle or Vehicle-Trailer Combination

● 73,000 pounds ● Option to use the Federal Bridge Formula for up to 80,000 pounds

Gross weights between 73,001 and 80,000 pounds (the maximum legal weight without a special Department of Transportation permit) are only allowed through application of the bridge formula.

Calculating Gross Weight Under the Federal Bridge Formula

The bridge formula used as an alternative under Connecticut law is the same one used under federal law. In 1974, Congress enacted a law establishing permissible commercial vehicle weight, height, width, and length limitations for vehicles using the Interstate Highway System. It also adopted the so-called “bridge formula” to provide the methodology for determining appropriate maximum gross vehicle weights taking into account the number of axles the vehicle has and the distance between the most distant sets of axles. It is called the bridge formula because its purpose is to establish gross weight maximums that are appropriate for bridge designs on the Interstate System. (Gross weight has the greatest effect on bridges while axle weight has the greatest effect on pavement structures.)

Congress made the federal limits mandatory in 1982. States could not set maximum weight, height, width, and length limits below the federal maximums for vehicles using the Interstate Highway System. States that had higher limits could retain them, but were preempted from setting lower limits.

Typically under the formula, a vehicle's maximum allowable gross weight increases as its number of axles and its wheelbase increase. For example, a three-axle vehicle could have a maximum allowable gross weight of anywhere from 42,000 to 60,000 pounds. To weigh 60,000 pounds, the distance between the first and last axles would have to be at least 32 feet. With only a 30-foot wheelbase it would be limited to 58,500 pounds gross weight and with a 28-foot wheelbase it would only qualify for 57,000 pounds gross weight. A vehicle with a 32-foot wheelbase but five rather than three axles could have a gross vehicle weight of 68,000 pounds. The maximum allowable gross vehicle weight under the bridge formula is 80,000 pounds. This is typically possible when the vehicle is a five-axle combination vehicle with at least 51 feet between the first and last axle sets.

Axle Weights

Connecticut's maximum axle weights are the same for all sizes of commercial vehicles. A vehicle cannot have more than 22,400 pounds on a single axle or more than 18,000 pounds on axles that are spaced less than six feet apart. Thus the typical “tandem” axle on a truck is under a practical limitation of 36,000 pounds. The axle weight limits under federal law are more restrictive. Federal law allows only 20,000 pounds on a single axle and 34,000 on axles spaced less than six feet apart. Connecticut is allowed to have higher maximum axle weights because it had these weight limits in effect before Congress adopted the federal standards.

Connecticut law also provides a special exception for refuse collection vehicles. Commercial or municipal refuse hauling vehicles can exceed the axle weight maximum by up to 7,000 pounds as long as the combined weight on the rear axles does not exceed 44,500 pounds. The exception does not apply on roads that are part of the Interstate Highway System (CGS § 14-269a). The exception was established to help refuse collection vehicles accommodate the weight of the equipment that compacts the trash as it is collected.

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