The disruption is a result of a strike by the RMT Union.
Passengers at Irish Rail experienced two 24-hour strikes before Christmas as part of a dispute over pay.
Industrial action today follows strikes on Monday and Wednesday, affecting services run by Arriva Rail North (Northern) which runs services in Yorkshire, South Western Railway (SWR), Merseyrail and Greater Anglia.
"No one should be in any doubt, these disputes are about putting the safety of the travelling public before the profits of the private train companies".
RMT general secretary Mick Cash said: "Every single effort that RMT has made to reach negotiated settlements in these separate disputes with the different train operating companies over safe operation and safe staffing has been kicked back in our faces and we are left with no option but to confirm a further phase of industrial action in the New Year".
The RMT says it has concerns over safety and job losses due to Southern plans to bring in driver-only-operated trains.
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South Western Railway, which operates in areas including London Waterloo, Reading, Exeter and Southampton, said it expected to run more than 70% of its weekday timetable and would use longer trains to provide extra seats.
The company states: "These trains, and any replacement buses we run, are usually very busy".
"It is important that our customers plan carefully if they intend to travel today as we will have few services after 7pm".
Members of the Rail, Maritime and Transport (RMT) union were said to be "solidly supporting" walkouts at four train operators in the long-running dispute over the role of guards.
"If operators aren't planning to run any services whatsoever, then unfortunately you can't claim compensation".