Essential work on Woodhouse tunnel on the A58M inner relief road in Leeds will begin next month after final funding approval was confirmed by the Department for Transport (DfT).
Carillion was first earmarked for the job in December 2010.
The DfT has formally approved funding of £16.34m for the project, which is part of a wider £24.96m maintenance scheme of improvements to the inner ring road.
Two other structures on the road, New York Road viaduct and Lovell Park road bridge, have already had essential maintenance completed.
The DfT funding is supported by £8.6m provided by Leeds City Council, the West Yorkshire Local Transport Plan Fund, The University of Leeds and Leeds NHS Trust.
The work is needed to address deterioration of the tunnel over the past 40 years. Some critical repairs were carried out on the tunnel roof in the summer of 2011, but the remaining essential maintenance works are now required.
The project is expected to last approximately two years, with the majority of the works being carried out during night-time closure of the tunnel, from 7pm to 6am, Sundays to Thursdays.
Leeds City Council executive board member for development and the economy Councillor Richard Lewis said: "The Leeds Inner Ring Road is the most important road in the city in terms of keeping Leeds moving, so it is absolutely essential that any risk to its future is addressed.
"With more than 80,000 vehicles travelling through Woodhouse Tunnel every day, it is inevitable that it has suffered wear and tear in the 40 years since it was built and this scheme will mean it can continue to be used in a safe condition.”