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Bridge Roadway Safety for Agricultural Vehicles: Understanding Bridge Weight Limits

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Contact Information: Freight Feedback at FreightFeedback@dot.gov

United States Department of Transportation Federal Highway Administration

U.S. Department of Transportation
Federal Highway Administration
Office of Operations
1200 New Jersey Avenue, SE
Washington, DC 20590

FHWA-HOP-16-068

December 2016

Small brige on dirt road with no rails with a small stream under it.Collapsed wooden bridge with farm equipment on collapsed bridge.Wooden bridge with heavy mechanical equipment on it. Yellow mechanical structure appears to be tipped up and only on two wheels.

Transportation agencies rely on driver compliance to preserve and protect the Nation’s 60,000 weight-restricted bridges. Crossing a bridge in a vehicle that exceeds the weight limit can damage both the bridge and your vehicle, meaning you or other bridge users may not be able to cross safely. If your vehicle damages a bridge, you may be held liable for the cost of repair.

Small collapsed green wooden bridge with farm tractor overturned.

Preserve Bridges, Prevent Liability.

Not all bridges were designed to carry today’s maximum legal weight vehicles, including modern agricultural equipment. Also, some bridges have deteriorated over time, which reduces their load carrying capacity. Pursuant to the National Bridge Inspection Standards, bridges that cannot safely support all legal vehicles must be weight restricted. Through bridge weight limit signs, the traveling public receives notice of the maximum vehicle weight a specific bridge can safely support. The signs also help extend bridge service life by preventing damage and potential failures.

44 years - Average age of the Nation's 600,000 bridges. 10% - Percentage of the Nation's bridges* with weight restrictions. 80% - Percentage of the Nation's weight restricted bridges* located on local roadways where agricultural equipment commonly travels. Note: * Refers to bridges greater than 20 feet in length.

Many States have laws that allow larger agricultural equipment to operate on their roadways, but not all of the bridges on these roadways were designed to support such loads. A weight-restricted bridge cannot safely support the weight of any vehicles that exceed the posted weight limit even if they are otherwise legal on the adjacent roadways.

Know your vehicle and load, understand load posting signs, and obey the weight limits.

  1. It is your responsibility to know the weight and configuration of your vehicle and load.
    • If you do not know the weight of your vehicle and attached trailers, contact the vehicle manufacturer or check the weight at a local certified scale facility. Check gross load and maximum axle weight for both the empty weight and the weight at maximum capacity.
    • In some States, the actual weight may not exceed the declared gross weight on the vehicle registration.
    • Check with your State transportation agency to understand all applicable laws for your vehicles.
  2. It is your responsibility to understand and obey load posting signs.
    • Do NOT exceed the posted weight limit on any bridge.
    • Bridge weight restriction signs vary between States and localities. If you do not understand the signs in your area, contact the owner, which may be the local or State transportation agency.
  3. What if my vehicle and load exceed posted capacities? Do not cross the bridge! Instead:
    • Take an alternate route that can legally and safely carry your vehicles, or
    • Reduce your load and make multiple trips, or
    • Contact your local or State transportation agency to see if accommodations can be made to the bridge to allow you to cross safely.
  4. What are the consequences of violating a bridge weight limit sign?
    • Subjecting a bridge to vehicles that are heavier than the structure is able to carry safely can cause damage both visible and hidden, which could lead to closure or failure of the bridge.
    • You may be cited with a traffic violation for not obeying a regulatory sign.
    • You may be held liable for damages if you violate the load posting.

Weight limit signs carrying the legend WEIGHT LIMIT XX TONS are used to indicate the maximum gross vehicle weight (including equipment being towed by the vehicle) that can safely cross the bridge.

White road sign with black lettering that reads WEIGHT LIMIT 10 TONS.

Examples of other load posting signs.

White road sign with black lettering. Weight Limit. A small truck with 8T beside it. Then a large truck with trailer with 12T beside it. Then a truck with a double trailer with 16T beside it.A white road sign with black letters that reads WEIGHT LIMIT 2 TONS PER AXLE 10 TONS GROSS

An axle weight limit sign applies to axle weight rather than gross load. The sign may read AXLE WEIGHT LIMIT XX TONS or AXLE WEIGHT LIMIT XX LBS, indicating the maximum safe axle load of your vehicle and any equipment it is towing.

A white road sign with black letters that says AXLE WEIGHT LIMIT 5 TONS

The allowable Federal weight limit applies to bridges on the Interstate System and within reasonable access to it. On other roads, limits may be higher or lower as determined by State or local laws.

Common Bridge Load Posting Signs Compared to Common Vehicles. The data portrays different size vehicles and if they are safe to cross bridges of various size. Across the top axis are displayed the following vehicle types: Small Tractor (GVW 5-8 tons), Medium Tractor (GVW 15 tons), Dually Tractor (GVW 25 tons), Medium Tractor (15 GVW tons) PLUS Loaded Grain Cart (29 tons) = (GVW 44 tons), Tractor Trailer Loaded (GVW 36 tons). For A weight limit of 3 tons none are safe to cross. For a weight limit of 16 tons only the small tractor and medium tractor are safe to cross. For an axle weight limit of 10 tons only the small tractor and medium tractor are safe to cross. For weight limits of 20T, 24T and 28T, only the the small and medium tractors are safe to cross.

Image of large red and white vehicle with monster truck sized tires on a bridge. With workman before and after the vehicle.

Where can I get more information?

  1. Your local or State transportation agency.
  2. State oversize/overweight permitting offices. For a list of contacts for each State visit: https://ops.fhwa.dot.gov/freight/sw/permit_report/index.htm.
  3. State and locality specific websites for load posted bridges. For example: https://idrivearkansas.com/?show=weight_restricted_hwys.
  4. Your agricultural vehicle manufacturer.
  5. FHWA’s "Bridge Formula Weights" brochure. http://ops.fhwa.dot.gov/freight/publications/brdg_frm_wghts/bridge_formula_all_rev.pdf.
  6. FHWA’s Federal Size Regulations for Commercial Motor Vehicles guide. https://ops.fhwa.dot.gov/freight/publications/size_regs_final_rpt/size_regs_final_rpt.pdf.
  7. Wisconsin DOT Implements of Husbandry (IoH) Study Group. http://wisconsindot.gov/Pages/dmv/agri-eq-veh/study.aspx.

For More Information:

U.S. Department of Transportation
Federal Highway Administration
Office of Operations
1200 New Jersey Avenue, SE
Washington, DC 20590
Toll-Free "Help Line" 866-367-7487
www.ops.fhwa.dot.gov

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