In my crude way, my references to over-weight Americans has a point when looking at some of the high mileage cars, the Smart-for-two and compact cars. Lighter cars will get better mileage than their heavier breathern but it often comes at the expense of passenger and payload and no way matches hybrid payload specifications.
So sure, there are mini-cars and they fill a nitch:
But that is another redirection of hybrid skeptics, "Don't look at the interior space, just the highway mileage."
Cars, vehicles need to meet the owner requirements and that includes passenger and cargo capabilities. A vehicle that works in tropical Asia might not work in other areas. One of the better metrics is to ratio the payload versus operating expense as a true measure of vehicle economy ... results per unit of operation cost.
Bob Wilson