It's interesting how different the theoretical carbon saving/cost of doing something can be from observations of people doing it in real life.
Car ownership & use has a large carbon footprint, so living car-free ought to greatly reduce one's carbon footprint.
However...

This study by @JuuditO et al found that not owning a car frees up a lot of money to spend on other things. So the average middle-income Finnish driver giving up their car achieves only 32% of the expected carbon savings, and in some cases emit more once car-free than with car!

Those with the smallest carbon footprints, apparently, are those who have a car but barely use it. https://books.google.co.uk/books?hl=en&lr=&id=UlsyDwAAQBAJ&oi=fnd&pg=PT22&dq=Ottelin+J,+Heinonen+J+and+Junnila+S+2017+Nordic+Experiences+of+Sustainable+Planning:+Policy+and+Practice+ed+S+Kristjansdottir+(Abingdon:+Routledge)+Rebound+effect+for+reduced+car+ownership+and+driving&ots=hNEMXOjg6O&sig=VwXc8QDYHNln4kPaRXX_dTvOf_0&redir_esc=y#v=snippet&q=Rebound%20effect&f=false

However, the conclusion surely isn’t that everyone should have a barely used new car?
@JuuditO