Rail workers are said to be solidly supporting the latest strike in the long-running dispute over the role of guards on trains.
Members of the Rail, Maritime and Transport (RMT) union on South Western Railway (SWR) walked out on Friday for 72 hours.
It is the longest strike since the dispute started on SWR almost a year ago.
Picket lines were mounted outside stations and hundreds of services will be cancelled over the three days.
The company has said the industrial action is unnecessary as no guards will lose their jobs under its plans.
RMT general secretary Mick Cash said: ”RMT members are standing rock-solid and united again this morning across South Western Railway at the start of 72 hours of action in the campaign to put public safety, security and access before private profit.
“RMT is angry and frustrated that efforts by the union to get an agreement on the guard guarantee with South Western Railway bolted down has been repeatedly kicked back in our faces by a company that refuses to move the process on and address the fundamental issues.
“That is no way to treat a serious dispute that will impact on huge numbers of passengers throughout this weekend and SWR need to get out of this bunker mentality.
“Our members are striking today to put public safety before private profits and it’s about time SWR took note of what is going on elsewhere in the rail industry, and the settlements RMT has struck that underpin the guard guarantee, and started talking with us seriously around a similar package that puts safety, security and access to services top of the agenda.”