The whole idea of making train tickets extremly cheap is to make it "competitive" to cars. Trains are already cheaper to use than cars for a lot of people. But many people already own a car and have to pay the fixed costs per month anyway. Insurance, taxes, depreciation
If they plan a trip, the don't calculate the whole cost of ownershipt, they calculate the distance and how much fuel they need (a.k.a. flexible costs).
An extremely cheap ticket makes the car owners stop using their cars so much. This is not just a benefit for the abstact idea of "environment", but also a direct benefit for the population. Less cars means less noise pollution, less air pollution and more space on the roads. That way people, who actually need a car, van or truck to get around and do their work, benefit.
