Roadworks on Oxford's busy Abingdon Road look set to cost Oxford Bus Company £150,000 over the next eight months.
Repairs at Folly Bridge started this week and are already causing major problems for bus passengers.
Some services are being delayed by more than 30 minutes as buses try to negotiate the area, where work is being carried out to repave footways.
Bus company bosses are frustrated that buses approaching from the east of the city are also being delayed due to roadworks off Cowley Road.
Journeys that should take just half-an-hour are taking more than an hour, according to bus managers.
The company is now bringing in extra buses and drivers to help maintain services and minimise delays.
Nigel Eggleton, Oxford Bus Company's commercial director, said: "It's essential for us to maintain services and reliability.
"It's very frustrating, as the bus company itself has no control over the timing of the road works and the congestion caused."
He added: "The cost of extra services will reach over £150,000 before the roadworks are completed."
Emergency measures include changes to the X3 service from Abingdon. The delays mean it will not be possible to serve the railway station until the roadworks are completed, at the end of October.
The X3 service will terminate at Castle Street and start again from Queen Street. Passengers travelling to or from the station can use the 5 service. X3 tickets will be accepted.
Services 16, 16A, 35, 35A and 35B going into the city will operate via Iffley Road.
From Friday, the Redbridge park-and-ride 300 service will travel into the city centre along Donnington Bridge Rd and Iffley Road.
Patrick Mulvahill, the county council's principal engineer, said bus companies had been consulted fully about the roadworks.
He added: "This is the last summer of roadworks for the Abingdon Road, because we have big jobs to do elsewhere.
"We do try to look after the bus companies, but if we don't fix the roads how are they going to travel?
"I'm surprised the Oxford Bus Company is suggesting its drivers are suffering such long delays, because traffic is flowing quite well at the moment."
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