MDT issues new load posting for Smith River Bridge

The Montana Department of Transportation recently issued a new load posting for the Smith River Bridge, five miles southeast of Ulm, on Milligan Road, in Cascade County.

The posting is part of a multi-year effort to update load ratings and postings on Montana bridges as mandated by the Federal Highway Administration, according to MDT.

The new posting on the Smith River Bridge applies to special hauling vehicles, limiting the maximum gross vehicle weight of single-unit vehicles with 6 or 7 axles to 31 tons.

“The FHWA mandate is in response to changes in the trucking industry over the last decade. Truck manufacturers are building specialized hauling vehicles capable of legally carrying heavier loads than typical vehicles have in the past. SHVs are single-unit, short-wheelbase, multiple-axle trucks commonly used in the construction, waste management, bulk cargo, and commodities hauling industries,” according to MDT.

These vehicle configurations concentrate heavy loads over a short length and have been found to overstress bridges beyond what was previously modeled by standard commercial vehicles, according to MDT.

In response, “FHWA has determined that all states must include these new, short, heavy vehicles when evaluating the safe limits of bridge capacity,” according to MDT.

MDT is currently updating load ratings for 4,500 public bridges statewide, including about 2,500 owned and maintained by MDT, to comply with the mandate. This effort is expected to take about two more years.

MDT has created an interactive map with statewide load posted bridge locations available here:

“Bridge weight restrictions are required when the engineering analysis of a bridge, known as a load rating, indicates that it cannot carry standard, legal loads. Load ratings provide information about how much distributed weight can safely pass over a bridge. Load posting signs show maximum weight limits for different vehicle types, depending on their axle configuration. A posted bridge is safe to use, but the weight of certain vehicles must be limited accordingly,” according to MDT.

More information on understanding and interpreting Montana’s weight limit signs and silhouettes can be found in MDT’s load posting brochure.

The exact location of the Smith River Bridge is viewable on Google Maps here.

For the most up-to-date information and additional resources, visit MDT’s Bridge Load Posting Program website.

For questions about the program or specific bridges, please call the project hotline at 1-888-824-8445 or email