Many of London's busiest commuter routes are being crippled on Tuesday as train drivers stage another strike.
Members of Aslef are launching a wave of fresh walkouts in a long-running dispute over pay.
Drivers are on strike at Southeastern, Southern/Gatwick Express, Thameslink, South Western Railway and Great Northern.
South Western Railway has urged passengers to only travel if "absolutely necessary" on Tuesday, warning that a significantly reduced service will operate on a limited number of lines.
Aslef's general secretary Mick Whelan says some drivers have not had a pay rise for almost five years and accused the Government of "giving up" trying to resolve the row.
The strikes were expected to be the first test of the minimum service levels legislation, aimed at ensuring train operators could run 40% of services - but none of the train companies are using the new law.
In a further blow to London travellers, the RMT has announced two 48-hour strikes on the London Overground, on February 19 and March 4.
Meanwhile commuters on the London Underground are facing fresh disruption with the Central Line suspended between North Acton and Ealing Broadway due to a points failure. The Tube's busiest line is once again suffering severe delays due to a shortage of trains.
