The closure of Portslade’s level crossing in two weeks is set to cause a weekend of travel chaos as trains are cancelled and traffic diverted.
No trains will run between Brighton and Littlehampton on Saturday, 30 and Sunday, 31 November, with replacement buses put on instead.
And Boundary Road will also be closed on both Saturday and Sunday, leading to diversions.
Lucy McAuliffe, Network Rail’s Sussex Route director said: “We’re replacing worn-out track in the Portslade area with new rails, sleepers, and ballast – the small rocks underneath the track that support the rails and the sleepers.
“This essential work will mean a safer and more reliable railway for passengers.
“To complete the work, we need to close the railway, and as the work is taking place near the level crossing, it needs to close as well. The underpass will remain open, and a shuttle bus is in place for the less mobile.
“We’re asking motorists to leave a bit more time to travel as the diversion will mean slightly journeys. Trains will be replaced by buses when the work is being carried out. Thank you for bearing with us while we work to improve the railway.”
Jenny Saunders, Southern’s Customer Services Director, said: “We thank passengers and road users for their patience while these essential works are under way.
“It means we won’t be running trains between Brighton and Littlehampton all day on Saturday, November 30 and Sunday, December 1.
“Instead, rail replacement buses will run between Brighton and Littlehampton. Please plan your journey ahead of time using the Southern website.”
The work begins at 1am on 30 November and ends at 2am on Monday 2 December. Motorists are advised to use the A270 Old Shoreham Road as a diversionary route.
The old underpass – a former cattle tunnel – will remain open for pedestrian use.
A shuttle bus will also be available for people with wheelchairs, pushchairs and those who are unable to make use of the underpass.
The bus will pick up and drop off between Portslade railway station car park, north of the level crossing (next to the cycle hub), and Portslade station (stop C) outside Station Kebab House.
The shuttle will operate from 1am on Saturday 30 November for 24 hours a day until the crossing reopens.
The number 6 and 46 buses will be diverted via Old Shoreham Road, Olive Road and Portland Road. Route 1X will run via route 1 using Station Road, A259 and Church Road in both directions.
Rail services that usually run between London Victoria and Littlehampton will be diverted to terminate at Brighton only.
Trains will continue to run between Littlehampton and Portsmouth Harbour or Southampton Central.