Rail engineering works are affecting trains out of Brighton this weekend and next.
Replacement buses are running between Brighton and Three Bridges on the Brighton to London main line.
Network Rail said that the engineering works had been scheduled for yesterday (Saturday 21 March), today (Sunday 22 March) and next Saturday and Sunday (28 and 29 March).
The company said: “Network Rail will be making improvements to signalling on the Brighton main line this weekend and next, to increase capacity and reliability.
“As a result, buses will replace trains between Three Bridges and Brighton.
“Passengers are reminded to check before they travel either at National Rail Enquiries or with their train operator – Southern or Thameslink.
“Once the project to upgrade the line is complete, the lines around Balcombe and Haywards Heath will have a new signalling system to allow trains to run in both directions on both tracks, with new and more reliable equipment and a doubling of capacity from 6 to 12 trains per hour.
“These improvements to the Brighton main line are part of Network Rail’s ongoing programme of upgrade to the railway to accommodate the ever growing number of passengers taking the train.”