Bo’ness Road Bridge at the Chapelhall junction, on the A8 east of Glasgow, was removed over two weekends in May.
Engineers worked round the clock on the project to take out the bridge over the dual carriageway because it is two narrow for the new M8.
The B799 between Chapelhall and Holytown will be diverted over a new bridge spanning both the A8 and M8.
The work is part of the £500 million upgrade of the M8, M73 and M74 outside Glasgow.
Further changes to contraflows and the closure of sliproads and junctions on the A8 start on Friday.
The A8 past the Shawhead junction will be reduced to one lane in each direction with a contraflow from Friday to Monday.
Sliproads on and off the westbound carriageway at Newhouse - where the A8 meets the M8 at junction six - will close for six months from Monday, 5 September.
New westbound sliproads at the Chapelhall junction will open on the same date.
Graeme Reid, Transport Scotland’s project sponsor for the M8 M73 M74 Motorway Improvements Project, said: “We are now seeing extensive traffic management on the A8 to allow the construction of the new M8 and to link the new carriageways and junctions to the existing road network.
“Consequently, this will result in delays.
“Whilst we’re doing everything we can to minimise the disruption, changes to traffic management layouts will result in delays.”