> it is very hard to make a small 4 stroke engine No, actually it's not. That's nonsense. You can buy today a 5 hp 4 stroke outboard engine, weighing about 25

> it is very hard to make a small 4 stroke engine No, actually it's not. That's nonsense. You can buy today a 5 hp 4 stroke outboard engine, weighing about 25 kg (including transmission, housing, controls etc), for $1300 brand new. http://www.ebay.com/bhp/5-hp-outboard-motor http://www.ebay.com/bhp/5-hp-outboard-motor Furthermore, what you are proposing is not new: a tiny car with a tiny engine for one person. That's called a microcar. Wikipedia has a long list of these, starting from the 1950's onward to today, some of which have sold in quite large numbers: https://en.wikipedia.org/wiki/Microcar https://en.wikipedia.org/wiki/Microcar A modern, electric example is the Reva (G-Wiz in the UK), which was produced from 2001 to 2012. https://en.wikipedia.org/wiki/REVAi https://en.wikipedia.org/wiki/REVAi Given that these already exist, why are they not the solution to our problems? For one, they're well-documented death traps. They use a loophole by classifying as a four wheel motorbike, meaning they don't need to be crash tested. Also, they are a replacement for only a small part of what a real car does, and this is the part that's also most easily replaced by public transport.