Work on the A602 near Watton-at-Stone is set to be completed later this summer.
Hertfordshire County Council and contractor Tilbury Douglas have been working to resolve issues with the Dane End bridge.
Defective prefabricated beams were installed on the bridge last year, and concerns about the bridge's structure were raised.
New replacement beams have now been installed, and much of the deck reinforcement has also been installed.
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The new concrete deck is due to be poured in June, and the county council has said it expects the new A602 road alignment and the bridge to be "fully open in summer 2023".
In the meantime, traffic will continue to run on the current A602 alignment.
The ongoing works are part of the county council's A602 Improvement Scheme.
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