The other dynamic to consider is the shift to ride sharing. Somebody who commutes in their private vehicle every day is unlikely to change to a different mode of transport, but an uber rider is more likely to switch to a different mode.
Also, increasing ridership helps to make public transit better, which actually can convince car drivers to switch. in my town, the bus comes every 30 minutes except during special events like festivals when they get a couple extra buses and it comes every 10 minutes. At a 30min frequency, i take my car or bike. at a 10 minute frequency, i take the bus. If you increase the number of riders by making transit free, that can create a political motivation to increase transit service.
Also, increasing ridership helps to make public transit better, which actually can convince car drivers to switch. in my town, the bus comes every 30 minutes except during special events like festivals when they get a couple extra buses and it comes every 10 minutes. At a 30min frequency, i take my car or bike. at a 10 minute frequency, i take the bus. If you increase the number of riders by making transit free, that can create a political motivation to increase transit service.