A FRESH alert has been issued to train passengers amid fears that many have not cancelled plans this weekend despite strike action.

Only a fifth of services are running as 40,000 members of the RMT union at Network Rail and 13 train operators walk out for the third day this week.

Operators are telling passengers they should “only travel by train if necessary” and to check their journey in advance.

Many commuters were able to avoid the disruption caused by strikes on Tuesday and Thursday by working from home.

But people with long-standing plans to travel by train today, Saturday – such as for a day trip or holiday, a visit to friends or relatives, or to attend an event – may be keen to press ahead with their trip despite the industrial action.

A rail industry source told the PA news agency that while stations were “relatively quiet” during the first two strike days, there is “a nervousness” about what will happen on Saturday.

Services across Britain will primarily be restricted to main lines, but even those will only be open between 7.30am and 6.30pm.

That means first trains will leave later and last trains will be much earlier than normal.

Passengers are being warned to expect a Sunday service which includes no trains before 7.15am from Tuesday, June 21 and Sunday, June 26.

A Southern Rail spokesman said: “Between Tuesday June 21 and Sunday June 26 inclusive the railway will operate limited opening hours with services starting later and finishing much earlier than usual.

“On strike days, the last trains will finish late afternoon. Please check your first and last trains carefully, as there will be no alternative travel outside of these services.

“As this industrial action is affecting the whole country, we will be unable to provide alternatives such as replacement buses and ticket acceptance with other local rail and bus operators.

“We recognise that it will be very difficult to travel and our advice, regrettably, is to travel only if your journey is absolutely necessary.”

Govia Thames Railway (GTR) workers are not on strike but Southern is running an amended timetable to ensure a “reliable and consistent service”.

This will impact all journeys, including on Southern, Gatwick Express and Thameslink this weekend.