As we mentioned earlier, the X-Prize foundation recently commissioned a survey of Americans that found, surprisingly enough, that sixty-two percent of them were very interested in buying a vehicle that could get 100mpg. Seventy-six percent of the respondents also thought the development of such vehicles would be important to the United States. None of this is a shock, nor is the fact that more than twice as many people cited the cost of highly efficient vehicles over any other reason for not buying them.
I just wanted to add sometime to the earlier post: the vehicles most likely to be practical for daily use that could achieve anywhere near that 100mpg threshold in the near term will use some sort of battery for energy storage. Unfortunately one look at the price of a Tesla Roadster or the manufacturing cost (as opposed to the heavily subsidized price) of a Phoenix SUT will tell you that cost will remain a stumbling block for some time. The cost of those high capacity lithium batteries is still the biggest block to vehicles like the Chevy volt being produced.
[Source: Automotive X-Prize]