A stretch of main road in Reading is to remain closed for sewer repairs until the end of May.
Thames Water closed the A4 Bath Road by Liebenrood Road on 1 May and originally estimated repairs would last a week.
But the firm said the damage to pipes was worse than expected.
Reading Buses said it supported the repair work but the road closure had created "the worst traffic situation imaginable" at peak times.
The bus company's head, James Freeman, said the closure in both directions had caused bus delays of up to an hour.
He added the closure had a knock-on effect on other congested areas of Reading and was causing "real problems some distance away" on the Tilehurst Road and Oxford Road.
Thames Water spokeswoman Becky Trotman said: "The more we dig, the more damaged sewer pipe we find."
The firm needs to repair at least 20m (65ft) of pipe, which is 5.5m (18ft) underground.