Strike action by 170 guards at Merseyrail seeking a 35-hour week has brought rail traffic on the region's network to a complete standstill.
The strike is the second in the RMT union dispute which involves an ongoing argument over compensation for rest days.
The 48-hour strike could cause disruption to the crowds expected to make their way to Aintree for this weekend's Grand National.
RMT general secretary, Bob Crow, said: "Our members have once more given a magnificent show of solidarity on the picket-line.
"This strike is even more effective than the first, and Merseyrail appears to have given up all attempts at running any sort of service."