The Highways Agency is carrying out the six-month programme between the junction with the A4185 at Chilton and the A4130 Milton Interchange in both directions.
The improvements, which start on Monday 1 December, include the replacement of filter drains, pipes and gully connections as well as the clearing and cleaning of the drainage network and ditches. The work will result in fewer unplanned road closures caused by the need for emergency road maintenance.
To carry out this necessary work safely, narrow lanes and a 50mph speed limit will be in place 24 hours a day with overnight lane closures and occasional overnight carriageway closures, all of which will be published in advance.
Highways Agency Service Delivery Manager Guy Watts said:
This work will provide smoother and safer journeys for users of the A34 in this part of Oxfordshire.
Road users will benefit from a section more resistant to flooding and therefore less likely to impact upon journeys.
While work of this nature inevitably causes some inconvenience, we will aim to prevent as much disruption as possible.
This scheme has been planned with the cooperation and input of local authorities and emergency services.
Members of the public should contact the Highways Agency Information Line on 0300 123 5000.
Journalists should contact the Highways Agency press office on 0844 693 1448 and use the menu to speak to the most appropriate press officer.