Train users in South Yorkshire have been warned to expect delays today because of strike action on the railway.
The union RMT has organised a second day of industrial action this week, which will affect Northern services between 7am and 7pm today.
The industrial action is over the union's safety concerns as private train operators press ahead with plans for 'driver only' operations.
A spokesman for train operator Northern, which is affected by the strike, said: "To help keep our customers moving we aim to run over 1,200 services on each strike day.
"The majority of available trains will operate between 7am and 7pm, with services on some routes finishing earlier.
"During these hours the overall number of trains running will be significantly reduced. We expect trains and any replacement buses we operate will be extremely busy. Please allow extra time for journeys, plan carefully and consider whether travel is necessary."