Public transportation tends to be much cheaper for riders than private transportation is for drivers. A year-long ticket for Munich is around $1000. At current prices, that won't even buy you 10k miles worth of gas in a compact car, to say nothing of the price of the car itself, insurance and repairs.

I say that to say this, if people have more money in their pocket, they will tend to spend more money, so the difference could easily be made up in sales tax on all the newly-freed-up disposable income.