Limited train services have been reinstated between Oxford and Radley at peak times after the line was closed due to emergency repairs to a bridge.
Around three morning and three evening trains are now running between the two stations.
A Didcot to Culham service has also been announced.
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But the line remains closed to through services with the reopening of the route planned for June 10.
Network Rail shut the railway between Oxford and Didcot last month after it was reported that the Nuneham Viaduct over the River Thames was sinking.
This, coupled with the closure of Botley Road at the rail bridge, has led to significantly increased traffic around Oxford at rush hour.
A spokesman for Great Western Railway said: “It has always been our intention to provide as many rail services as we are able to, where track (and any other limitations) enable us to do so.
“Yesterday (May 2) we began trialling limited peak time train shuttle services either side of Nuneham Viaduct.
"The first operating between Oxford and Radley, and the second between Didcot Parkway and Culham.
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“These complement the rail replacement bus services already in operation, which will continue.
“If this works well we will continue to operate the shuttle rail services through to June 10 when the line is set to reopen."
The services are being loaded into journey planners overnight by Network Rail, and customers can check their journey at www.gwr.com/check each morning.
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