This disregards how systems interacts with each other. For instance how more car traffic in cities leads to economic decline (because there is less people shopping, it's gotten less hospitable to walk downtown).

I don't think car traffic leads to economic decline. It changes how people spend their time.

Let's say in 15 minutes, I can walk 1 km, go 5 km on a bike, 10 km with a public transport and 15 km with a car.

Area = pi * radius*2 Walking = 3.14sqkm Bike = 78sqkm Public transport = 314sqkm Car = 706sqkm (All is just example ignoring parking, looking for bike stands, waiting for public transport or changing stations)

If I want to do Yoga, and it is in 706sqkm around me, but not in 314km, I have to use car and no other transport is going to get me there in 15 minutes. When the city have a policy that prohibits me from using the car, I need to choose the second most preferred activity, which might be for example going to a café nearby.

Cities that slow down transport are in fact harming people's interests by limiting their choices and pushing them to suboptimal choices. (Which also inherently means that faster is always better and people who want to slow down traffic in cities are evil, but that off-topic)

If there were no subsidies for cars, public transport and bike lines and all this was based purely on contributions from users, it would create a self-optimising feedback mechanism. Going to yoga could for example cost $2 to build & maintain roads. I might not want to spend it and I might go to a café instead because everyone living in the city already pays for his sidewalk anyway.

Students shouldn't be funding universities, they lack the funds for anything substantial. University graduates makes more sense imo.

In the end, graduates are going to pay for it. But I wouldn't necessarily tie the university with its graduates. What if somebody drops-off? What if, in the future, students will be able to combine classes (and get credits) from 3 universities via online lessons? Each uni can have different system of student debt.

I think, paying per class or year (but rather class) and having student debt as a separate instrument (that can be private or public), is much better.

"punishes good behaviours (saving and investing),"

Depends on who is defining "good". Consumerism drives economies and some might not want to encourage saving.