Commuters using Southern Rail services have been facing long delays during the first day of strike action today.
Conductors working for the company are protesting over a safety dispute, with 14 days of strike action planned between today and Christmas.
Many trains between Portsmouth, Southampton, London and Brighton have been delayed or cancelled.
Passengers have been taking to Twitter to vent their frustrations at the services.
User Hana Peterside tweeted: ‘Today I couldn’t get on the overcrowded 7:56 from EC to Victoria -1/2 people left on the platform. Avoid Southern if u can @SouthernRailUK.’
And Thomas Sunesson posted: ‘@SouthernRailUK abandoned ec station. Stood there for 30 mins. The 2 trains that came were packed. Now on train from west Croydon. Refund?’
The RMT union has been locked in a bitter dispute with Govia Thameslink Railway (GTR) for most of 2016 over plans to change the role of guards to on-board supervisors, which would see drivers open and close train doors on most of its network.
Staff have already held five walkouts this year totalling eight days.
There will be strikes from today until Thursday.
Three day strikes will also start on Tuesday October 18, Thursday November 3, Tuesday December 6, and a two-day walkout would start on Tuesday November 22.