HELENA, Mont. — The Montana Department of Transportation (MDT) has begun implementation of new load posting procedures on public bridges across the state as mandated by the Federal Highway Administration (FHWA). As a result, motorists may soon start to notice new weight limits and signs on some bridges. The postings are part of recently updated federal requirements for bridge load rating and posting.
Bridge weight restrictions are required when the engineering analysis of a bridge, known as a load rating, indicates that the structure cannot carry standard, legal loads. Load ratings provide information about how much distributed weight can safely pass over a bridge. Load posting is required when a load rating indicates that a bridge cannot safely carry certain loads that would otherwise be legal in the state of Montana. Load posting signs show maximum weight limits for different vehicle types depending on axle configuration.
“Many older bridges were never designed to carry vehicle types that have become common in present-day use, and some bridges have deteriorated over time,” said Stephanie Brandenberger, bridge engineer for MDT. “Bridge weight restriction signs are posted to keep motorists safe and to ensure that the bridge remains functional. We need to prevent heavy loads from crossing and over stressing the bridge, which can lead to both visible and hidden damage.”
MDT is currently updating load ratings for 4,500 public bridges across the state, including about 2,500 that are owned and maintained by MDT. The effort is expected to take about four years to complete. Brandenberger emphasized that posted weight restrictions do not mean a bridge is unsafe — as long as vehicles crossing the bridge meet posted limitations.
“MDT needs the public’s help in understanding and following weight restrictions — for their own safety, but also to help maintain bridge integrity and safeguard bridge longevity,” she said.
To assist with public outreach and education, MDT is creating interactive maps and other information available for the public, as the bridge load posting program continues. For the most up-to-date information and additional resources, visit MDT’s Bridge Load Posting Program website. For questions about the program or information about specific bridges, call the project hotline at 888-824-8445 or email [email protected].