What It Means
A posted bridge is a structure that has been evaluated by an engineer under the AASHTO Manual for Bridge Evaluation and found incapable of safely carrying one or more standard legal loads, resulting in signed weight restrictions at both approaches. Posting signs typically specify maximum allowable weights in tons for three vehicle categories: single unit (two-axle trucks), combination (tractor-trailer), and tractor-trailer combinations, though some states use different categories. The NBI captures posting status in Item 41 (Structure Open, Posted, or Closed): code A (Open, no restriction), B (Open, posting recommended but not legally implemented), D (Open, would be posted except for Emergency Public Interest), E (Open, temporary shoring), G (New bridge not yet opened), K (Bridge closed to all traffic), P (Posted for load), and R (Posted for other load-capacity reason). Approximately 13% of U.S. bridges (roughly 80,000 bridges) are posted or have some form of restriction. Rural county-owned bridges in the Midwest and Appalachia have the highest posting rates, often above 25%, because older timber and light steel structures were designed for horse-drawn or early automotive loads far below modern HL-93 design vehicles. Posted bridges create significant economic costs: agricultural cooperatives must reroute grain trucks, school districts must alter bus routes, logging operations face detour miles that add fuel cost, and emergency responders may lose access to entire neighborhoods. FHWA's Bridge Formula Program under the IIJA specifically targets posting and replacement of off-system rural bridges with $27.5 billion in formula funding over five years, with a specific set-aside for bridges on public roads that are not on the federal-aid highway system.
Frequently Asked Questions
What does "Posted Bridge" mean?
A bridge with signed weight restrictions prohibiting vehicles above a specified gross weight from crossing.
Why does Posted Bridge matter for bridge safety?
A posted bridge is a structure that has been evaluated by an engineer under the AASHTO Manual for Bridge Evaluation and found incapable of safely carrying one or more standard legal loads, resulting in signed weight restrictions at both approaches. Posting signs typically specify maximum allowable w...