BRIDGES: D-minus

Most bridges are designed and constructed on the assumption of a lifespan of 40 to 60 years. Nearly one-third of the bridges on Idaho’s state system (574) have reached the half-century mark and another 522 will turn 50 years of age within the next decade.

“This means that 50 percent of the bridges on the state highway system will be 50 years old or older by 2016, which will likely translate into additional needs for maintenance and funding,” according to ASCE.

A similar scenario exists for bridges that serve local routes. More than 25 percent of the 2,371 bridges (605) already are 50 years old and another 502 will reach that mark by 2021.

Capacity component grade: B
Condition component: B
Funding component: D-minus
Future need component: D-minus
Operation and maintenance component: C
Public safety component: C
Resilience component: D


  • Additional funding for the top 60 critical bridges needs to be addressed immediately.
  • The backlog of bridges that need to be replaced because of their age, in both the state and local highway systems, needs to be a focus by Idaho Transportation Department and the locals to catch up with the aging bridge inventory.
  • The long-term funding to support the bridge replacement program needs to be carefully studied so that bridges are replaced as they reach their life expectancy.


Published 3-16-2012