Heavy trucks have been banned from the U.S. Route 4 bridge over the Connecticut River between White River Junction and Lebanon, N.H.
Officials say inspectors have found significant corrosion on the bridge.
Starting Monday, heavy trucks were banned and alternating one-way traffic was implemented. More restrictions are possible.
The bridge was built in 1936 and rebuilt in 1976. It is scheduled to be replaced in 2010.
The bridge is on New Hampshire’s "Red List," which requires frequent inspections because of known deficiencies.