Plungington Road has been closed to vehicles (at the Rippon Street junction) for emergency repairs to a sewer.
United Utilities started the work on August 30 to "prevent foul flooding."
Lancashire County Council has said that the closure is scheduled to last until September 12.
And Preston Bus has advised its passengers that during the closure one of its key services will be diverted.
The number 23 will operate via Fylde Road, Brook Street, Blackpool Road, then Plungington Road and normal route. Inbound to the city the reverse of this route will be used.
The company has advised that Adelphie Street and Plungington Road (between Aqueduct Street and Blackpool Road) will not be served. Passengers should use the Brook Street stops instead.
A spokesman for Preston Bus said: "Apologies for any inconvenience. As soon as we get further information, we will keep customers informed."