The effects of Tuesday's strike have caused train services to be disrupted.

What passengers should expect from the PA news agency is answered here.

Will there be any trains running today?

Around 40% of the services will be able to operate.

If there is no strike today, why aren't timetables back to normal?

The start of trains was delayed because signallers and control room staff walked out of work.

How long do trains usually leave depots?

Between 3 and 4 am.

Passengers services usually start at a certain time.

Between 5 and 6 a.m.

Today, how has that changed?

signallers on daytime shifts started taking trains out of depots at 6am.

The start of services was delayed.

It was expected to take several hours in some places.

How soon will the services start ramping up?

London services will increase quickly because trains don't have to travel long distances from depot to stations.

It will take a long time in some places.

Will services come back to normal today?

Even during the day, the service will stay thinner than usual and some operators will wind down services earlier than normal.

What about the following day?

The picture will be the same as Tuesday.

Half of lines will only be open during the morning and evening hours.

There is a chance that the strikes will be called off.

Passengers are still urged to check with the train operators for any updates to services.