Boaters have been warned that there will be a series of closures for navigation on the River Great Ouse near Offord while a temporary bridge used in the construction of the A14 upgrade is removed.
The structure had been used during the building of the new crossing of the Great Ouse, one of the key features of the £1.5 billion upgrade to the road, and is no longer needed.
Contractors are about to start pulling back the bridge which means the river has to be closed to users for a maximum period of two hours at a time, twice a week, over a period of about a month.
Highways England, which is behind the scheme, is timing the closures for off-peak periods between 7am and 9am in order to minimise disruption to users.
It said that river users could moor at Offord and Brampton locks and that updated signage showing expected durations for the work would be in place.
A spokesman for the Environment Agency, which is responsible for advertising the closures, said: "Essentially we have put out a navigation notice, which is common practice for us when we need to let boaters know of circumstances which might impact their journeys.
"In this case it is worth noting that temporary moorings will be available for boaters who may experience slight delays."
The spokesman added: "Navigation will still be possible but they should use caution and follow signs and instructions from the contractors and traffic marshals."
The work on removing the temporary bridge is expected to take place between September 2 and October 6.
Work on building the long-awaited A14 upgrade began in November 2016 and the road is expected to be ready by the end of 2020.
It involves 21 miles of upgraded road, widening stretches and junction improvements, together with a 12-mile bypass between Brampton and Swavesey, involving the construction of a new stretch of road and the widening of the section of the A1 between Brampton and Alconbury.