Energy considerations
As a physicist and energy management consultant, I always start with energy considerations. Is there enough energy in a gallon of fuel to run the car 70 miles? With careful driving and a well-designed, lightweight vehicle, the answer is yes. Can it be done with normal driving in a combined city/highway cycle? Doubtful. Can it be done while having fun with all that acceleration or driving at speeds over 100 mph? No! I want to see some actual performance numbers accompanied by a description of the driving conditions and verified by a competent, reputable organization other than the manufacturer.
