Hunger Hill junction in Poole is switching to a new one-way system road layout on West Quay Road and West Street.
Over the weekend motorists are being urged to use sat navs with caution when in Poole town centre, while the new road layout is being introduced.
The switch over will begin at 7am on Sunday as part of an £11m project to improve the busy Hunger Hill junction.
Work on the junction began in October and is expected to take nine months to complete.
The improvements are part of a project to improve access to the Port of Poole and open up sites for redevelopment.