BRISTOL/PORTSMOUTH — Starting Thursday, Dec. 29, the maximum vehicle weight allowed on the Mt. Hope Bridge will be changed from 40 tons to 30 tons, the R.I. Turnpike and Bridge Authority (RITBA) has announced.

The modified weight allowance is due primarily to a Federal Highway Administration load rating manual update. It’s also required because of an “as-built” design factor which has existed since the bridge opened in 1929, according to RITBA. The as-built factor involves the outside girders, some of which were reinforced with steel plates approximately 50 years ago.

The reduction in maximum vehicle weight is not related to bridge maintenance or the upcoming dehumidification project, RITBA says.

RITBA is coordinating with the R.I. Department of Transportation’s bridge and traffic engineers to identify and communicate detour routes for impacted drivers. RITBA is also doing outreach to the municipalities and commercial enterprises affected by the new restrictions to ensure that emergency vehicles and freight carriers are aware of the new weight limit posting.