New Load Posting Issued on Thirty Mile Creek Bridge

BLAINE COUNTY, Mont. (NMB) – The Montana Department of Transportation (MDT) recently issued a new load posting for the Thirty Mile Creek Bridge, in Harlem, on Main Street North, in Blaine 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 (FHWA).

The new posting on the Thirty Mile Creek Bridge applies to SHVs; it limits the maximum gross vehicle weight of single-unit vehicles with 4, 5, 6, or 7 axles to 25 tons.

The FHWA mandate is in response to changes in the trucking industry over the last decade. Truck manufacturers are building specialized hauling vehicles (SHVs) 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.

These SHV configurations concentrate heavy loads over a short length, and they have been found to overstress bridges beyond what was previously modeled by standard commercial vehicles. To account for their increasing presence and ensure safe operation, FHWA has determined that all states must include these new, short, heavy vehicles when evaluating the safe limits of bridge capacity.

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

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.

Further information on understanding and interpreting Montana’s weight limit signs and silhouettes can be found in MDT’s load posting brochure, located here:

The exact location of the Thirty Mile Creek Bridge is viewable on Google Maps here:

To assist with public outreach and education about the bridge load posting program, MDT has created an interactive map with statewide load posted bridge locations available here:

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

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

Alternative accessible formats of this document will be provided on request. Persons who need an alternative format should contact the Office of Civil Rights, Department of Transportation, 2701 Prospect Avenue, PO Box 201001, Helena, MT 59620. Telephone 406-444-5416 or Montana Relay Service at 711.

Courtesy of MDT

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