The exit 49 on-ramp to I-495 south will be closed during the early hours of Thursday to allow for deliveries of reinforcing steel for the new southbound bridge.
There will also be double right lane closures on I-495 south between exits 49 and 48 Thursday, Jan. 21, from 2-5 a.m. The Massachusetts Department of Transportation said lanes will be closed to allow for installation of the steel.
When the on-ramp near Westgate Center closes, traffic will be detoured to exit 50, Broadway, Route 97.
The schedule is weather dependent and subject to change.
Following completion of the northbound bridge last October, traffic in both directions along the highway was rerouted. Southbound traffic now crosses the median and shares the northbound bridge, while demolition of the remaining 1960s-era bridge over the Merrimack River takes place.