Weekend Cotswold Line train services in mid-July will be affected by engineering work between Charlbury and Moreton-in-Marsh.
Network Rail is replacing life-expired track in the Evenlode area, south of Moreton-in-Marsh.
On the weekends of Saturday, July 16, and Sunday, July 17, and Saturday, July 23, and Sunday, July 24, buses will replace trains between the two stations and call at Kingham en route.
On the Saturdays, some buses will also serve Shipton station, stopping on the A361 at the top of the station approach road.
GWR train services will continue to operate between London, Oxford and Charlbury, and between Moreton-in-Marsh, Worcester and Great Malvern.
A few direct trains linking Hereford and Worcester with Reading and London will run via Swindon both weekends.
Passengers should check train and bus times before travelling and allow extra time for their journeys. Timetables are available in online journey planners.
And further track renewal work on the weekends of September 10-11, 17-18 and 24-25, plus October 1-2, means trains will not be able to run through the Oxford area.
Cotswold Line trains will operate between Great Malvern, Worcester and Hanborough, with bus links available to and from Oxford and Didcot Parkway, where passengers can connect with trains to and from Reading and London Paddington.
Chiltern Railways services between London Marylebone and Oxford will start and terminate at Oxford Parkway during these weekends.
Click here for more details of these changes.