Now this might not seem to be about micro cars, but if you do drive one regularly, and if you cycle or use public transport regularly you can expect a reasonable score.
On the website below you can create an avatar for yourself and answer various questions about your home, car, diet, possessions etc., then at the end you get a number which tells you how many Earths it would take to sustain the world's population at your standard of living. It takes about 5 minutes, is quite fun, and very interesting. It's new, and at present you can only choose America or Australia as your home. Choose Aus, because there a some extra choices e.g. for cyclists. I saw this on a drum forum, and have posted it on a ukulele forum. Most Europeans get 2.5 to 5, Americans are more around 5-8. I have a pretty modest diet and life-style, cycle a lot, or use the Trojan which is very economical, and when I do drive it is almost always with others, and yes I am a veggie which helps hugely. I suggest you click on the bottom half of the pics for the more detailed breakdown. Strongly recommended!
www.footprintnetwork.org/en/index.php/GFN/page/caculators/