The RMT union is planning a national protest rally in London to mark the second anniversary of its dispute with Southern.
The demo, to be held on Wednesday 25 April, marks two years of strikes over the role of guards on trains.
The dispute follows the introduction of driver-only operation on Southern trains and the guards becoming “on-board supervisors”.
Previously, the guards were responsible, among other things, for shutting the train doors.
This is now done by the drivers, meaning that trains need not be cancelled if there is no guard or conductor.
The RMT fears for the future of about 400 guards working for Southern and many more across the country, with other train operating companies following suit.
The union complained that Southern brought in the changes without agreement, contrary to its deal with staff, choosing instead to impose new terms or make staff redundant.
On Southern alone, 40 days of strike action have taken place, most recently on Monday 12 March.
The dispute has been settled in Scotland. Merseyrail has agreed to arbitration. The union remains in dispute with Southern, Arriva Rail North, Greater Anglia and South Western.
The union said that the dispute is about Southern putting profit before safety as well as access for passengers with disabilities.
RMT general secretary Mick Cash said: “Our members have stood solid and united for two years in the fight for passenger safety and access on Southern Rail in Britain’s longest-running industrial dispute.
“The sheer grit and determination of our members on Southern to put public safety before private profit over the past two years of this dispute is a credit to the trade union movement and the communities they are standing up for.
“We are now receiving regular reports of trains running without a guard or on-board supervisor on Southern Rail and of disabled passengers being denied support and access and the routine safety of passengers being compromised.
“The scandal of Southern Rail, mirrored in disputes on SWR (South Western), Merseyrail, Northern and Greater Anglia, cannot be allowed to continue and these companies should get out of their bunkers and get back round the table with the union.”
Andy Bindon, human resources director at Southern’s parent company, Govia Thameslink Railway, said: “We urge the RMT to finally bring to an end this pointless industrial action.
“The changes they are objecting to were introduced on Southern more than a year ago, and their members have been working this way ever since, resulting in a more efficient service with more on-board staff and fewer cancelled trains.
“Southern ran a normal service on most of its routes in the latest day of action.
“The RMT has staged 40 days of strikes on a mandate that is more than two years old and we have made numerous offers to them – none of which have been put to their members.”