Hull City Council has insisted that its controversial roadworks on the city's County Road North cannot be delayed.
The busy road has been shut while urgent repairs are carried out on the flyover.
Some local residents have criticised the decision to close the flyover, while others have questioned why the road should be closed ahead of Hull Fair.
But councillor Martin Mancey said work to strengthen the structure needed to be carried out as soon as possible.
Beginning the repairs this week means the work will not be delayed by cold weather and will prevent any disruption for retailers ahead of the festive season, he added.
Coun Mancey told the Yorkshire Post that the flyover has been weakened by salt in the winter, and said there was a danger of concrete falling onto the Hull to Bridlington and Scarborough railway line below.
He said: "If a chunk of concrete dropped off on a train it could be a lot more serious than a bit of traffic congestion."
Roadworks are also being carried out on Bricknell Avenue, Thwaite Street, in Cottingham and Park Street.
Traffic has also been affected by Northern Power Grid repairing cables on Chanterlands Avenue, but the council said this work has now been suspended.
Copyright Press Association 2012