A nine-day closure of a major railway line has begun, causing major disruption for passengers.
No trains will operate on the southern end of the Brighton Main Line (BML) until February 25 to enable Network Rail to carry out engineering work as part of a £67 million project.
The closure, which began on Saturday, is affecting Three Bridges services between Brighton and Lewes.
No trains are serving eight stations including Haywards Heath, Burgess Hill and Hassocks.
Network Rail warned that journeys would be “significantly longer” and trains which do run will be “much busier than usual”.
The BML is normally used by 300,000 people each day and connects the south coast with London on Southern and Thameslink trains.
Services to and from Brighton are being diverted along the coast via Littlehampton, adding an hour to journeys.
A replacement bus and coach service is in operation, featuring more than 240 vehicles every day.
Derby County supporters were among those disrupted as they travelled to watch their team’s FA Cup fifth round match against Brighton and Hove Albion on Saturday.
Demand for the alternative services and routes will be increased on Monday morning when commuters embark on their journeys to work.
Research by watchdog Transport Focus indicated that 52% of passengers support the work and 47% are satisfied with the information provided.
More than three out of four (76%) planned to take action such as working from home, taking annual leave or avoiding peak travel times.
Network Rail claimed reliability on the BML would deteriorate if it did not carry out the work.
The closure is timed to coincide with half-term as fewer passengers use the railway during school holidays.
John Halsall, Network Rail’s managing director for the South East route, said: “This work is absolutely critical as this stretch is one of the most unreliable parts of the network, accounting for half the delays to trains arriving from the south into central London.
“We know it’s never a good time to close the railway, but the only alternative would have been to close the line for 84 weekends over the course of two years.
“Doing the work over this nine-day period means we can achieve so much more and deliver the punctuality and reliability benefits to passengers much sooner, plus the railway is much quieter during the school holidays.
“Working with our colleagues at Govia Thameslink Railway, we are making every effort to enable those passengers who need to travel during this period to do so comfortably.”
Network Rail is renewing and upgrading track junctions and signalling, shoring up embankments and installing technology to detect potential problems before they occur and help services recover faster when there is a fault.
Extensive work is being carried out within four Victorian tunnels to stop leaks and drainage issues which cause major delays.
Parts of the BML will also be closed during several additional weekends until May.