Drivers are being warned that there will be “short term pain for long term gain” as a main route into Huntingdon is closed to traffic for six weeks.
The warning comes after it was announced that the route under the railway bridge in Ermine Street will be blocked 24 hours a day from 5am on Monday, February 1, until Monday, March 14.
The closure is to allow Network Rail to carry out a second phase of work to strengthen the bridge.
A spokesman for Network Rail said: "The reason it is going to be six weeks is because it is short term pain for long term gain. Workers will need to work on it 24 hours a day otherwise if they were stopping and starting it would go on for months. "They will be going in and hitting it hard and hopefully won't have to come back for another 30 to 40 years."
The closure will mean that drivers looking to travel to and from the town centre will face a three-mile diversion via St Peter's Road to be able to get to Stukeley Road.
Concerned district and county councillor Mike Shellens said: "Originally Network Rail requested a full closure for six months. This has been cut back to just six weeks, but will still have a major impact. It is highly possible that there will be very severe delays at peak hours."
The road under the bridge will be closed to vehicles but pedestrians, cyclists and emergency service vehicles will still be able to continue under the bridge.
Councillor Tom Sanderson said: "The impact of this is going to be quite big for the people who use this route but it is something that needs to be done because if it is not, and something happens down the line, questions are going to be asked."
The first phase of work saw the road closed during the evening and at weekends but many drivers experienced tailbacks around the ring road and onto George Street.
Rob McIntosh, route managing director at Network Rail, added: "Improvements like the work we're doing to Ermine Street bridge keeps passenger and freight services running, which ultimately benefits the economies of the towns and cities served by the railway."