What is the purpose of bridge load rating and how are overweight vehicles evaluated?

• A. Load rating is only used during construction.
• B. Load rating assesses a bridge’s capacity to safely carry traffic; overweight vehicles are evaluated against capacity margins, with permits if margins exist.
• C. Overweight vehicles are never permitted; no evaluation is needed.
• D. Load rating has no practical use.

Answer: (B)

Bridge load rating tells us how much load a bridge in its current condition can safely carry for typical traffic. It’s a practical tool used to manage road safety and material integrity, guiding decisions about which vehicles can cross and under what conditions.

When a vehicle is heavier than the standard design load, engineers check the bridge’s rating to see if there is any margin between capacity and the actual load. If there is a comfortable margin, a permit can be issued that allows the overweight vehicle to cross, usually with restrictions such as route, timing, speed, or an escort. If there is little or no margin, or if the bridge is in poorer condition, crossing may be restricted or denied, or it may require structural upgrades before permitting the overweight vehicle.