Guards at South Western Railway will walk out on strike again at midnight.
It’s the fourth of eight days of action in the latest wave of protests against plans to change working practices.
SWR says it will use managers to keep as many services running as possible but hundreds of trains will be cancelled.
Peace talks earlier this week ended without agreement.
SWR want to operate trains without a guard in exceptional circumstances like disruption and sickness.
The RMT union say it is unsafe, a claim which is denied by the company.
RMT strike action is planned on the following dates:
0001 Hours and 2359 Hours on Saturday 4 August 2018
0001 Hours and 2359 Hours on Saturday 11 August 2018
0001 Hours and 2359 Hours on Saturday 18 August 2018
0001 Hours on Friday 31 August 2018 and 2359 Hours on Saturday 1 September 2018
All the latest updates can be found on the South Western Railway website.