Passengers are advised to check before travelling tomorrow (February 23) as gale force winds from Storm Doris are due to hit the south.
Gusts may reach 70mph causing possible damage to buildings, power cuts and toppling trees.
“Doris Day” – as the storm has been dubbed – is set to be the worst of the winter.
As a result, there will be changes to some Southern, Southeastern and Gatwick Express services.
Network Rail said: “Speed restrictions are used to keep passengers and staff safe during high winds, as trees and other objects can get blown onto the tracks.
Top speed of 50mph
“With trains running at a reduced top speed of 50mph, drivers are better able to bring trains to a halt if anything is spotted ahead.”
Andy Derbyshire, chief operating officer, Network Rail South East route, said: “Gale force winds are forecast on Thursday, so we’re putting a 50mph speed limit in place when winds are strongest to limit the risk to passengers and staff should trees or other objects get blown onto the tracks.
“This is part of our standard planning for stormy weather, but it will mean changes to journeys for some passengers. Your safety is our top priority, so thank you for your understanding and please check before you travel.”
Cancellations and delays
A Southern spokesperson said: “These speed restrictions will mean that we won’t be able to run our full service on some of our routes, leading to cancellations and delays. Our advice is to check before you travel for the latest information about your train.”
The Met Office has placed Sussex in a “Be Aware” swathe of the country; sometimes called a “yellow warning”.
It is valid from 6am to 8pm on Thursday.
Some very strong winds are expected with gusts of 60 to 70mph likely; stronger over hills and coasts.
Power cuts possible
The Met Office said the strongest winds could be short lived but said “damage to structures, interruptions to power supplies and widespread disruption to travel networks are likely, with a danger of injury from flying debris.
“Trees are also likely to be damaged or blown over.”
Heavy rain is also expected.