For the next three months, Germans will be able to travel the country for just €9 (£7.50; $9.50) a month in a drive to tackle the soaring cost of living.
All local and regional transport on trains, buses and metro is included in the government’s initiative, although inter-city trains are not.
The cheap tickets are also aimed at getting people to leave their cars. However, fuel tax has also been reduced by around 30 cents a litre for petrol, bringing prices down below €2.
The tax has been brought down to the EU minimum, again for the next three months, so diesel prices are also being cut by around 14 cents a litre.
Transport Minister Volker Wissing has described the €9-a-month tickets as a great opportunity: “It’s a success that we’ve already sold seven million tickets.”
However, rail company Deutsche Bahn is already struggling with overcrowding, delays and cancellations and the prospect of millions of extra passengers has prompted criticism of the plan.
Fewer than 70% of long-distance trains were on time in April, but Mr Wissing says the rail network is only running at 80% capacity. No major rail problems were reported in the hours after the scheme kicked in on Wednesday morning.
As in much of the rest of the world, Germans have been hit by rising energy prices, with inflation up to 7.9% last month. Chancellor Olaf Scholz told members of the German parliament on Wednesday that the main cause of the increase in prices was Russia’s invasion of Ukraine.
The federal government, which includes the Green party, has promised Germany’s 16 state authorities €2.5bn in compensation for the extra costs expected in staffing and fuel.
Although the €9-ticket does not include inter-city travel, it is possible to cross the country using regional trains.