You might spot new trains passing through Newtown on Sunday - but you won't be able to use them.
Transport for Wales and Network Rail will be installing new signalling on the Cambrian Railway for new trains due to run on the line. But the railway will be closed for the day to allow testing.
Buses will instead run between Aberystwyth and Shrewsbury, calling at Caersws, Newtown and Welshpool.
"Network Rail is upgrading the signals on the Cambrian Line to allow for the operation of our brand new trains. Trains will be in operation on this line to test the signal upgrade, but for safety reasons will not be for public use. We apologise for any inconvenience caused," said a statement.