Chiltern Railways has warned that trains between Oxford and London Marylebone will be 'extremely busy' from Monday 17th April.
The line between Oxford and Didcot is currently closed over concerns that the Nuneham Viaduct is sinking.
Network Rail closed the line suddenly on 3rd April over what they have described as a 'sudden and unexpected' deterioration of the viaduct.
Engineers are currently working around the clock to fix the problem.
Great Western Railway is unable to operate any trains on the line until 10th June at the earliest when it is expected to open. Hence, Chiltern Railways is currently the sole option for rail travel between Oxford and the capital for those not using replacement bus services.
Chiltern Railway say they have worked hard to increase capacity on this route from Monday 17th April onwards, including adding additional seats and carriages to services where possible.
But they still expect these services to be much busier than usual.
They are advising customers to consider alternative travel routes if possible, such as starting your journey from:
Didcot Parkway for direct services to London Paddington.
Bicester North or Haddenham and Thame Parkway for services to and from London Marylebone.
Stations between Oxford and London Marylebone may also experience additional crowding and some short-term changes to train times due to the ongoing disruption.
These include Haddenham and Thame Parkway, High Wycombe, and Beaconsfield.