Have you bought machinery equipment or have cargo you want to haul, but don’t know if your truck and trailer combination is legal? We get it.
In Pennsylvania, the maximum permitted gross weight for a truck or bus is 73,280 pounds and this regulation is designed to ensure road safety, infrastructure protection, and fair usage of transportation systems.
But understanding gross weight and how the cargo is distributed on a trailer are important factors to understand so do not get pulled over by police and receive a fine.
Here’s a detailed explanation of how this weight limit works.
Understanding Gross Weight
Gross Vehicle Weight (GVW) is the total weight of the vehicle, including the chassis, body, engine, fuel, accessories, passengers, and cargo.
For commercial vehicles like trucks and buses, maintaining the GVW within legal limits is crucial for safety and compliance.
Trucks can weigh up to a maximum of 80,000 pounds on interstate highways, assuming they have sufficient axles and proper spacing. However, for vehicles traveling on state highways in Pennsylvania, the specific weight limits can vary based on road classifications, bridge conditions, and the truck’s axle configuration.
The 73,280-pound maximum gross weight typically applies to commercial trucks and buses operating within Pennsylvania. This includes large freight trucks, tractor-trailers, and passenger buses.
Here is how the state breaks it down:
No combination shall, when operated upon a highway, have a gross weight exceeding the following:
- Two-axle truck tractor & single-axle semitrailer – 58,400 pounds
- Two-axle truck & two-axle semitrailer – 73,280 pounds
- Three-axle truck tractor & single-axle semitrailer – 73,280 pounds
- Two-axle truck & two-axle trailer – 73,280 pounds
Note: “truck” is your typical F250 type vehicles while “truck tractor” is your larger semi.
This limit helps prevent excessive wear and tear on roads and bridges, reduces the risk of accidents caused by overloading, and ensures that vehicles can operate safely without undue strain on their mechanical systems.
Calculating Gross Weight
To ensure compliance with the 73,280-pound limit, operators must accurately calculate the GVW:
- Vehicle Weight: Start with the unladen weight of the vehicle (the weight without any cargo or passengers).
- Cargo and Passengers: Add the weight of all cargo, passengers, and any additional equipment or modifications.
- Total GVW: Ensure that the sum does not exceed 73,280 pounds.
Example Calculation:
- Unladen vehicle weight: 30,000 pounds
- Cargo weight: 40,000 pounds
- Passengers and equipment: 3,280 pounds
- Total GVW: 30,000 + 40,000 + 3,280 = 73,280 pounds
But this calculation is often too simple when you add in how the weight is distributed over the truck and its axels. This is where the Bridge Formula comes in.
What is Bridge Formula?
Pennsylvania uses the Federal Bridge Formula set by the Federal Highway Administration (FHWA) to determine the maximum allowable weight for trucks based on the number of axles and the spacing between those axles.
The formula is designed to control not only the total weight of a truck but also how that weight is distributed over its axles while ensuring that vehicles crossing bridges do not exceed weight limits that could damage the bridge’s structure.
Here is how the equation is written: W=500((LN/N−1)+12N+36)
- W = Maximum weight in pounds that can be carried on a group of two or more axles
- L = Distance in feet between the outermost axles of the group (also known as the bridge length)
- N = Number of axles in the group
- Axle Weight = The weight that each individual axle is carrying. Spreading weight over more axles reduces stress on individual axles and bridge structures.
- Axle Spacing = The distance between the axles. The farther apart the axles are, the more the weight can be distributed across the vehicle, reducing concentrated loads on the bridge.
- Bridge Length = The distance between the first and last axles of a group (or the entire truck). A longer vehicle with more axles generally allows for a higher weight limit.
For example, a truck with 5 axles and a wheelbase (bridge length) of 51 feet can carry significantly more weight than a shorter truck with the same number of axles. The weight distribution across the axles helps minimize the risk of overloading the bridge structure.
Maximum Weight and Axle Weight Limits
As we said earlier, trucks can weigh up to a maximum of 80,000 pounds on interstate highways, assuming they have sufficient axles and proper spacing. However, for vehicles traveling on state highways in Pennsylvania, the specific weight limits can vary based on road classifications, bridge conditions, and the truck’s axle configuration.
Let’s consider a 5-axle truck (standard semi-truck) with axle spacing of 50 feet:
- L = 50 feet (distance between the outermost axles)
- N = 5 axles
Using the Bridge Formula, we calculate the maximum allowable weight.
This truck can carry up to 79,250 pounds, depending on specific bridge limits and Pennsylvania regulations.
But you must also think about the max weight allowed on the axel types.
According to the rules, no vehicle or combination driven upon a highway can have a weight upon any axle: more than the lesser of the manufacturer’s rated axle capacity or the following applicable weight:
- Steering Axles – 20,000 pounds
- Single Axles – 20,000 pounds
- Tandem Axles, a.s. under 6 feet – 36,000 pounds
- Tandem Axles, a.s. 6 to 8 feet – 40,400 pounds
- Tandem Axles, a.s. over 8 feet – 44,800 pounds
- Tridem Axles – 42,500 pounds
Exceeding Weight Limits and Permits
If a truck exceeds the calculated weight based on the Bridge Formula, it will require a special overweight permit in Pennsylvania.
These permits are issued on a case-by-case basis and usually involve routing the vehicle to avoid sensitive bridges and roadways.
Trucks that exceed weight limits without proper permits are subject to fines, penalties, and may be taken out of service until they are brought into compliance.
Handle all Licenses and Permits at once
Need help understanding the bridge formula? Need vehicle or trailer permits?
Reach out to CNS Licensing where we have been handling our clients’ licensing and permitting needs for over 30 years.
We offer several different services when it comes to titles including:
We also carry many types of plates for:
- Passenger Cars
- Trucks
- Motorcycles and Mopeds
- Trailers and Permanent Trailers
- Bus
- School Bus
- Intransit
- Omni Bus
- SME
- IMP
If you have any questions, call (717)627.4334 or email at info@cnslicensing.com.
