New measures have been deployed on board trains and at stations amid fears that more people might use public transport to return to work this week.
Security guards with crowd management training will be at some stations.
Passengers could be prevented from boarding a train or entering a platform if there are already too many people.
From Monday morning there will be more services as the railways move from a Sunday-style timetable to something similar to that of a normal Saturday.
More trains begin running but rail bosses worry that social distancing will not be possible on board.