The 9-euro ticket probably also relieves the burden on the streets during rush-hour traffic.
A current analysis by the traffic data specialist TomTom for the German Press Agency shows a decrease in the level of congestion in 23 of the 26 cities examined compared to the time before the introduction.
The data "suggests that this decline is related to the introduction of the €9 ticket," said TomTom traffic expert Ralf-Peter Schäfer.
"Commuters lost less time driving to and from work in June than in May in almost all cities surveyed."
Specifically, the experts compared the traffic jam levels in rush hour traffic on weekdays in calendar weeks 20 and 25 in 26 German cities.
The periods were chosen to avoid the effects of vacations and public holidays.
The result is clear: "In the first few days after the introduction of the 9-euro ticket, the data from TomTom showed hardly any effects of the measure on car traffic.
In the meantime, however, a positive effect on the flow of traffic can be seen in almost all cities in Germany," says Schäfer.
"The decrease in the loss of time varies from city to city," explained the expert.
The improvement in congestion levels was particularly strong in Hamburg and Wiesbaden.
There, the congestion level dropped by 14 and 13 points respectively.
This means that on a route that would take 30 minutes without traffic, drivers lost an average of 4.2 minutes less in Hamburg and 3.9 minutes less in Wiesbaden.
TomTom only observed slight deterioration in Kiel and Nuremberg.
In Karlsruhe, the level of congestion remained unchanged.