Children had to be taken to lessons, recreational activities, to see friends. Separate trips needed to be made to buy groceries, pick up laundry, etc. The scenario that Duany painted was one in which a member of the privileged upper middle class elite was virtually a prisoner of her transportation system. Often, the middle-class suburban mother's primary job today is serving as a chauffeur. This assessment of housewives as slaves to their cars presents a strong sociological indictment of the auto-based transportation system.
Additional criticism comes in the name of energy-efficiency and environmentalism.
If one accepts that optimizing energy use and minimizing environmental impact are critical aspects of sustainable design, an initial definition of a sustainable transportation system might be 'one that facilitates the greatest amount of human and social interaction using the least amount of non-renewable energy and creating the least amount of environmental damage. Clearly, in this light, the current auto-dominated transportation network is lacking. Nor will the solutions be found in more energy efficient vehicles alone. A solar-powered car, for example, may be made of completely recyclable materials, and may run solely on renewable energies, but if it implies a road infrastructure that eats up open space and promotes suburban sprawl with its ancillary social stratification and isolation, it cannot be said to truly meet the criteria for 'sustainability. Owning and operating the average car now costs 39.4 cents per mile, up 0.7 cents from last year.